Method of making functionalized substrates

ABSTRACT

Functionalized substrates, methods of making functionalized substrates, and methods of using functionalized substrates are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 11/611,246, filed Dec. 15, 2006, which claims the benefit ofpriority to U.S. provisional patent application Ser. No. 60/755,244entitled “METHODS OF MAKING FUNCTIONALIZED SUBSTRATES” filed on Dec. 30,2005, and U.S. provisional patent application Ser. No. 60/755,267entitled “FUNCTIONALIZED SUBSTRATES” filed on Dec. 30, 2005, the subjectmatter of both of which are incorporated herein in their entirety.

TECHNICAL FIELD

The present disclosure relates to functionalized substrates.

BACKGROUND

There is a need in the art for polymeric substrates having enhancedfunctionality. Further, there is a need in the art for methods of makingpolymeric substrates having enhanced functionality.

SUMMARY OF THE INVENTION

The present invention is directed to functionalized substrates andmethods of making functionalized substrates. More specifically, thefunctionalized substrates include a porous base substrate that has beenmodified to provide different functionality and/or reactivity, differentaffinity (i.e., increased or decreased) for one or more compounds, or acombination thereof.

Methods of making a functionalized substrate are provided. In someembodiments, the method comprises the steps of providing a porous basesubstrate having interstitial and outer surfaces; imbibing the porousbase substrate with a first solution to form an imbibed porous basesubstrate, the first solution comprising at least one grafting monomerhaving (a) a free-radically polymerizable group and (b) an additionalfunctional group comprising an ethylenically unsaturated group, an epoxygroup, an azlactone group, an ionic group, an alkylene oxide group, orcombination thereof; and exposing the imbibed porous base substrate to acontrolled amount of electron beam radiation so as to form a firstfunctionalized substrate comprising grafted species attached to thesurfaces of the porous base substrate, wherein at least one of thegrafted species comprises the additional functional group.

In other embodiments, the method comprises the steps of providing aporous base substrate having interstitial and outer surfaces; imbibingthe porous base substrate with a first solution to form an imbibedporous base substrate, the first solution comprising at least onegrafting monomer having (a) a free-radically polymerizable group and (b)an additional functional group comprising an ethylenically unsaturatedgroup, an epoxy group, an azlactone group, an ionic group, an alkyleneoxide group, or combination thereof; positioning the imbibed porous basesubstrate between a removable carrier layer and a removable cover layerto form a multilayer structure; exposing the multilayer structure to acontrolled amount of electron beam radiation so as to form afunctionalized substrate positioned between the removable carrier layerand the removable cover layer, the functionalized substrate comprisinggrafted species attached to the surfaces of the porous base substrate,wherein at least one of the grafted species comprises the additionalfunctional group; and removing the carrier layer and cover layers fromthe multilayer structure.

These and other features and advantages of the present invention willbecome apparent after a review of the following detailed description ofthe disclosed embodiments and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described with reference to theappended figures, wherein:

FIG. 1 depicts exemplary method steps for making functionalizedsubstrates of the present invention; and

FIG. 2 depicts exemplary method steps for making functionalizedsubstrates of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the present invention is herein described in terms of specificembodiments, it will be readily apparent to those skilled in this artthat various modifications, rearrangements, and substitutions can bemade without departing from the spirit of the invention. The scope ofthe present invention is thus only limited by the claims appendedhereto.

Functionalized substrates and methods of making functionalizedsubstrates are described. Various functional groups or species aregrafted onto the surfaces of a porous base substrate. These graftedfunctional groups or species often alter the surface properties orreactivity of the porous base substrate.

I. Functionalized Substrates

Compared to the porous base substrate before surface modification, thefunctionalized substrate typically has a different functionality and/orreactivity, a different affinity (i.e., increased or decreased) for oneor more compounds, or a combination thereof. Components of thefunctionalized substrate and physical properties of the functionalizedsubstrate are described.

A. Functionalized Substrate Components

The functionalized substrate comprises a number of components including,but not limited to, (a) a porous base substrate having interstitial andouter surfaces and (b) grafted species extending from the surfaces ofthe porous base substrate. Exemplary components for forming thefunctionalized substrates of the present invention are provided below.

1. Porous Base Substrate

The functionalized substrate comprises a porous base substrate. Suitableporous base substrates include, but are not limited to, porousmembranes, porous nonwoven webs, and porous fibers. The porous basesubstrate may be formed from any suitable polymeric material. Suitablepolymeric materials include, but are not limited to, polyolefins,poly(isoprenes), poly(butadienes), fluorinated polymers, chlorinatedpolymers, polyesters, polyamides, polyimides, polyethers, poly(ethersulfones), poly(sulfones), polyphenylene oxides, poly(vinyl acetates),copolymers of vinyl acetate, poly(phosphazenes), poly(vinyl esters),poly(vinyl ethers), poly(vinyl alcohols), and poly(carbonates). Suitablepolyolefins include, but are not limited to, poly(ethylene),poly(propylene), poly(1-butene), copolymers of ethylene and propylene,alpha olefin copolymers (such as copolymers of 1-butene, 1-hexene,1-octene, and 1-decene), poly(ethylene-co-1-butene) andpoly(ethylene-co-1-butene-co-1-hexene). Suitable fluorinated polymersinclude, but are not limited to, poly(vinyl fluoride), poly(vinylidenefluoride), copolymers of vinylidene fluoride (such as poly(vinylidenefluoride-co-hexafluoropropylene), and copolymers ofchlorotrifluoroethylene (such aspoly(ethylene-co-chlorotrifluoroethylene). Suitable polyamides include,but are not limited to, poly(imino(1-oxohexamethylene)),poly(iminoadipoyliminohexamethylene),poly(iminoadipoyliminodecamethylene), and polycaprolactam. Suitablepolyimides include, but are not limited to, poly(pyromellitimide).Suitable poly(ether sulfones) include, but are not limited to,poly(diphenylether sulfone) and poly(diphenylsulfone-co-diphenyleneoxide sulfone). Suitable copolymers of vinyl acetate include, but arenot limited to, poly(ethylene-co-vinyl acetate) and such copolymers inwhich at least some of the acetate groups have been hydrolyzed to affordvarious poly(vinyl alcohols).

In one exemplary embodiment, the porous base substrate comprises amicroporous base substrate having an average pore size that is typicallyless than about 1.0 microns. Suitable microporous base substratesinclude, but are not limited to, microporous membranes, microporousnonwoven webs, and microporous fibers. The microporous base substrate isoften hydrophobic and comprises one or more of the above-mentionedpolymeric materials.

In some embodiments, the porous base substrate is a hydrophobicmicroporous membrane such as a thermally-induced phase separation (TIPS)membrane. TIPS membranes are often prepared by forming a solution of athermoplastic material and a second material above the melting point ofthe thermoplastic material. The second material is a liquid above themelting point of the thermoplastic material. Upon cooling, thethermoplastic material crystallizes and phase separates from the secondmaterial. The crystallized thermoplastic material is often stretched.The second material is optionally removed either before or afterstretching. Microporous membrane are further disclosed in U.S. Pat. Nos.4,539,256, 4,726,989, 4,867,881, 5,120,594, 5,260,360, 5,962,544, and5,962,544, all of which are assigned to 3M Company (St. Paul, Minn.),the subject matter of all of which is hereby incorporated by referencein its entirety. Some exemplary TIPS membrane comprise poly(vinylidenefluoride) (i.e., PVDF), polyolefins such as poly(ethylene) orpoly(propylene), vinyl-containing polymers or copolymers such asethylene-vinyl alcohol copolymers and butadiene-containing polymers orcopolymers, and acrylate-containing polymers or copolymers. For someapplications, a TIPS membrane comprising PVDF is particularly desirable.TIPS membranes comprising PVDF are further described in U.S. PatentApplication Publication No. 2005/0058821, which is assigned to 3MCompany (St. Paul, Minn.), the subject matter of which is herebyincorporated by reference in its entirety.

In other embodiments, the porous base substrate is a non-woven web. Forexample, the nonwoven web can be prepared from ethylene-vinyl alcoholcopolymers as described in U.S. Pat. No. 5,962,544.

Both hydrophobic and hydrophobic microporous membranes are commerciallyavailable, for example, from Millipore Corp. (Billerica, Mass.) underthe trade designation “DURAPORE” and “MILLIPORE EXPRESS MEMBRANE”; orfrom Pall Corp. (East Hills, N.Y.) under the trade designation “NYLAFLO”and “SUPOR”.

2. Grafted Species

The functionalized substrate has grafted species attached to thesurfaces of the porous base substrate. The grafting of materials to thesurface of the porous base substrate often results in an alteration ofthe surface properties or reactivity of the porous base substrate. Thematerials that are grafted to the surface of the porous base substratesare typically monomers (i.e., grafting monomers). The grafting monomersusually have both (a) a free-radically polymerizable group and (b) atleast one additional function group thereon. The free-radicallypolymerizable group is typically an ethylenically unsaturated group suchas a (meth)acryloly group or a vinyl group. The free-radicallypolymerizable group typically can react with the surface of the porousbase substrate when exposed to an electron beam. That is, reaction ofthe free-radically polymerizable groups of the grafting monomers withthe surface of the porous base substrate in the presence of the electronbeam results in the formation of grafted species attached to the porousbase substrate. One or more grafting monomers may be grafted ontointerstitial and outer surfaces of the porous base substrate to tailorthe surface properties to the resulting functionalized substrate.

In addition to having a free-radically polymerizable group, suitablegrafting monomers typically have an additional functional group selectedfrom a second ethylenically unsaturated group, an epoxy group, anazlactone group, an isocyanato group, an ionic group, an alkylene oxidegroup, or combination thereof. The additional functional group canprovide a site of further reactivity or affinity. That is, in someembodiments, after the grafting monomer has been attached to the porousbase substrate through a reaction involving the free-radicallypolymerizable group, the additional functional group of the resultinggrafted species can be reacted further. For example, the additionalfunctional group can react to form a linkage group between the porousbase substrate and other materials such as other monomers ornucleophilic compounds having at least one nucleophilic group. In otherexamples, the additional functional group can impart a desired surfaceproperty to the functionalized substrate such as affinity for aparticular type of compound. If the grafted species contains an ionicgroup, the functionalized substrate will often have an affinity forcompounds having an opposite charge. That is, compounds with negativelycharged groups can be attracted to a functionalized substrate havinggrafted species with a cationic group and compounds with positivelycharged groups can be attracted to a functionalized substrate havinggrafted species with an anionic group. Further, the grafted species canimpart a hydrophilic surface to the functionalized substrate thatincludes a porous base substrate having a hydrophobic surface prior tosurface modification with the grafted species. That is, the graftedspecies contain an alkylene oxide group can impart a hydrophiliccharacter to the resulting functionalized substrate.

Some grafting monomers have a (a) free-radically polymerizable groupthat is a first ethylenically unsaturated group and (b) an additionalfunctional group that is a second ethylenically unsaturated group.Suitable grafting monomers having two ethylenically unsaturated groupsinclude, but are not limited to, polyalkylene glycol di(meth)acrylates.The term polyalkylene glycol di(meth)acrylate is used interchangeablywith the term polyalkylene oxide di(meth)acrylate. The term“(meth)acryl” as in (meth)acrylate is used to encompass both acrylgroups as in acrylates and methacryl groups as in methacrylates.Exemplary polyalkylene glycol di(meth)acrylates include polyethyleneglycol di(meth)acrylate monomers and polypropylene glycoldi(meth)acrylates monomers. Polyethylene glycol diacrylate monomerhaving an average molecular weight of about 400 g/mole is commerciallyavailable, for example, under the trade designation “SR344” andpolyethylene glycol dimethacrylate monomer having an average molecularweight of about 400 g/mole is commercially available under the tradedesignation “SR603” from Sartomer Co., Inc., Exton, Pa.

In one exemplary embodiment, the grafted species result from thereaction of a polyethylene glycol di(meth)acrylate monomers with theporous base substrate upon exposure to an electron beam. These graftingmonomers can be used to change a hydrophobic porous base substrate intoa hydrophilic functionalized substrate due to the presence of thepolyalkylene oxide group. In one desired embodiment, the polyethyleneglycol di(meth)acrylate monomers comprise a polyethylene glycoldimethacrylate monomer (e.g., polyethylene glycol dimethacrylate havingan average molecular weight of about 400 g/mole) alone or in combinationwith other monomers. The resulting functionalized can have a number ofdesired properties such as instant wettability following exposure to 1NNaOH for 20 hours as described in more detail below.

Some grafting monomers have a (a) free-radically polymerizable groupthat is a first ethylenically unsaturated group and (b) an additionalfunctional group that is an epoxy group. Suitable grafting monomerswithin this class include, but are not limited to, glycidyl(meth)acrylates. This class of grafting monomers can provide afunctionalized substrate having at least one epoxy group available forfurther reactivity. The epoxy group can react with other reactants suchas another monomer or with a nucleophilic compound to impart a desiredsurface property to the porous base substrate (e.g., affinity for aparticular compound or functional group having different reactivity).The reaction of the epoxy group with a nucleophilic compound, forexample, results in the opening of the epoxy ring and the formation alinkage group that functions to attach the nucleophilic compound to theporous base substrate. The nucleophilic compound typically contains atleast one nucleophilic group. Suitable nucleophilic groups for reactingwith epoxy groups include, but are not limited to, primary amino groups,secondary amino groups, and carboxy groups. The nucleophilic compoundcan contain additional nucleophilic groups that can crosslink multipleepoxy groups or can contain other optional groups that can impart ahydrophilic character to the functionalized substrate. The linkage groupformed by ring-opening of the epoxy group often contains the group—C(OH)HCH₂NH— when the epoxy is reacted with a primary amino group or—C(OH)HCH₂O(CO)— when the epoxy is reacted with a carboxy group.

In some embodiments, the epoxy groups can be reacted with amultifunctional amine such as a diamine having two primary amino groupsor a triamine having three primary amino groups. One of the amino groupscan undergo a ring opening reaction with the epoxy group and result inthe formation of a linkage group that contains the group —C(OH)HCH₂NH—between the nucleophilic compound and the porous bases substrate. Thesecond amino group or the second and third amino groups can import ahydrophilic character to the functionalized substrate or can crosslinktwo or more grafted species by reacting with one or more additionalepoxy groups. In some examples, the multifunctional amine is apolyalkylene glycol diamine or polyalkylene glycol triamine and reactionwith an epoxy group results in the attachment of a grafted specieshaving a polyalkylene glycol group (i.e., polyalkylene oxide group). Thepolyalkylene glycol group as well as any terminal primary amino grouptends to impart a hydrophilic character to the functionalized substrate.

Other grafting monomers have a (a) free-radically polymerizable groupthat is an ethylenically unsaturated group and (b) an additionalfunctional group that is an azlactone group. Suitable grafting monomersinclude, but are not limited to, vinyl azlactone such as2-vinyl-4,4-dimethylazlactone. This class of grafting monomers canprovide a functionalized substrate having at least one azlactone groupavailable for further reactivity. The azlactone group can react withother reactants such as another monomer or with a nucleophilic compoundto impart a desired surface property to the porous base substrate (e.g.,affinity for a particular compound or functional group having differentreactivity). The reaction of the azlactone group with a nucleophiliccompound, for example, results in the opening of the azlactone ring andthe formation of a linkage group that functions to attach thenucleophilic compound to the porous base substrate. The nucleophiliccompound typically contains at least one nucleophilic group. Suitablenucleophilic groups for reacting with an azlactone group include, butare not limited to, primary amino groups, secondary amino groups andhydroxy groups. The nucleophilic compound can contain additionalnucleophilic groups that can crosslink multiple azlactone groups or cancontain other optional groups that can impart a hydrophilic character tothe functionalized substrate. The linkage group formed by ring-openingof the azlactone group often contains the group —(CO)NHCR₂(CO)— where Ris an alkyl such as methyl and (CO) denotes a carbonyl.

In some embodiments, the azlactone groups can be reacted with amultifunctional amine such as a diamine having two primary amino groupsor a triamine having three primary amino groups. One of the amino groupscan undergo a ring opening reaction with the azlactone group and resultin the formation of a linkage containing the group —(CO)NHCR₂(CO)—between the nucleophilic compound and the porous base substrate. Thesecond amino group or second and third amino groups can import ahydrophilic character to the functionalized substrate or can crosslinkmultiple grafted species. In some examples, the multifunctional amine isa polyalkylene glycol diamine or a polyalkylene glycol triamine andreaction with an azlactone group results in the attachment of a graftedspecies having a polyalkylene glycol group (i.e., polyalkylene oxidegroup). The polyalkylene glycol group as well as any terminal primaryamino group tends to impart a hydrophilic character to thefunctionalized substrate.

Still other grafting monomers have a (a) free-radically polymerizablegroup that is an ethylenically unsaturated group and (b) an additionalfunctional group that is an isocyanato group. Suitable grafting monomersinclude, but are not limited to an isocyanatoalkyl (meth)acrylate suchas 2-isocyanatoethyl methacrylate and 2-isocyanatoethyl acrylate. Thisclass of grafting monomers can provide a functionalized substrate havingat least one isocyanato group available for reactivity. The isocyanatogroup can react with other reactants such as another monomer or with anucleophilic compound to impart a desired surface property to thefunctionalized substrate (e.g., affinity for a particular compound orfunctional group having different reactivity). The reaction of anisocyanato group with a nucleophilic compound can result in theformation of a urea linkage if the nucleophilic group is a primary aminoor secondary amino group or in the formation of a urethane linkage ifthe nucleophilic group is a hydroxy group. The nucleophilic compound cancontain additional nucleophilic groups that can crosslink multipleisocyanato groups or can contain other optional groups that can impart ahydrophilic character to the functionalized substrate. The linkage groupformed by reaction of a nucleophilic compound with an isocyanato groupoften contains the group —NH(CO)NH— when the nucleophilic group is aprimary amino group or —NH(CO)O— when the nucleophilic group is ahydroxy.

Yet other grafting monomers have a (a) free-radically polymerizablegroup that is an ethylenically unsaturated group and (b) an additionalfunctional group that is an ionic group. The ionic group can have apositive charge, a negative charge, or a combination thereof. With somesuitable ionic monomers, the ionic group can be neutral or chargeddepending on the pH conditions. This class of monomers is typically usedto impart a desired surface affinity for one or more oppositely chargedcompounds or to decrease the affinity for one or more similarly chargedcompounds.

Some exemplary ionic grafting monomers having a negative charge include(meth)acrylamidosulfonic acids of Formula II or salts thereof

In Formula I, R¹ is hydrogen or methyl; and Y is a straight or branchedalkylene (e.g., an alkylenes having 1 to 10 carbon atoms, 1 to 6 carbonatoms, or 1 to 4 carbon atoms). Exemplary ionic monomers according toFormula I include, but are not limited to, N-acrylamidomethanesulfonicacid, 2-acrylamidoethanesulfonic acid,2-acrylamido-2-methyl-1-propanesulfonic acid, and2-methacrylamido-2-methyl-1-propanesulfonic acid. Salts of these acidicmonomers can also be used. Counter ions for the salts can be, forexample, ammonium ions, potassium ions, lithium ions, or sodium ions.

Other suitable ionic grafting monomers having a negative charge includesulfonic acids such as vinylsulfonic acid and 4-styrenesulfonic acid;(meth)acrylamidophosphonic acids such as (meth)acrylamidoalkylphosphonicacids (e.g., 2-acrylamidoethylphosphonic acid and3-methacrylamidopropylphosphonic acid); acrylic acid and methacrylicacid; and carboxyalkyl(meth)acrylates such as 2-carboxyethylacrylate,2-carboxyethylmethacrylate, 3-carboxypropylacrylate, and3-carboxypropylmethacrylate. Still other suitable acidic monomersinclude (meth)acryloylamino acids, such as those described in U.S. Pat.No. 4,157,418 (Heilmann), incorporated herein by reference. Exemplary(meth)acryloylamino acids include, but are not limited to,N-acryloylglycine, N-acryloylaspartic acid, N-acryloyl-β-alanine, and2-acrylamidoglycolic acid. Salts of any of these acidic monomers canalso be used.

Some exemplary ionic grafting monomers that are capable of providing apositive charge are amino (meth)acrylates or amino (meth)acrylamides ofFormula II or quaternary ammonium salts thereof. The counter ions of thequaternary ammonium salts are often halides, sulfates, phosphates,nitrates, and the like.

In Formula II, R¹ is hydrogen or methyl; L is oxy or —NH—; and Y is analkylene (e.g., an alkylene having 1 to 10 carbon atoms, 1 to 6, or 1 to4 carbon atoms). Each R² is independently hydrogen, alkyl, hydroxyalkyl(i.e., an alkyl substituted with a hydroxy), or aminoalkyl (i.e., analkyl substituted with an amino). Alternatively, the two R² groups takentogether with the nitrogen atom to which they are attached can form aheterocyclic group that is aromatic, partially unsaturated (i.e.,unsaturated but not aromatic), or saturated, wherein the heterocyclicgroup can optionally be fused to a second ring that is aromatic (e.g.,benzene), partially unsaturated (e.g., cyclohexene), or saturated (e.g.,cyclohexane).

In some embodiments of Formula II, both R² groups are hydrogen. In otherembodiments, one R² group is hydrogen and the other is an alkyl having 1to 10, 1 to 6, or 1 to 4 carbon atoms. In still other embodiments, atleast one of R² groups is a hydroxy alkyl or an amino alkyl that have 1to 10, 1 to 6, or 1 to 4 carbon atoms with the hydroxy or amino groupbeing positioned on any of the carbon atoms of the alkyl group. In yetother embodiments, the R² groups combine with the nitrogen atom to whichthey are attached to form a heterocyclic group. The heterocyclic groupincludes at least one nitrogen atom and can contain other heteroatomssuch as oxygen or sulfur. Exemplary heterocyclic groups include, but arenot limited to imidazolyl. The heterocyclic group can be fused to anadditional ring such as a benzene, cyclohexene, or cyclohexane.Exemplary heterocyclic groups fused to an additional ring include, butare not limited to, benzoimidazolyl.

Exemplary amino (meth)acrylates (i.e., L in Formula II is oxy) includeN,N-dialkylaminoalkyl(meth)acrylates such as, for example,N,N-dimethylaminoethylmethacrylate, N,N-dimethylaminoethylacrylate,N,N-diethylaminoethylmethacylate, N,N-diethylaminoethylacrylate,N,N-dimethylaminopropylmethacrylate, N,N-dimethylaminopropylacrylate,N-tert-butylaminopropylmethacrylate, N-tert-butylaminopropylacrylate andthe like.

Exemplary amino (meth)acrylamides (i.e., L in Formula II is —NH—)include, for example, N-(3-aminopropyl)methacrylamide,N-(3-aminopropyl)acrylamide, N-[3-(dimethylamino)propyl]methacrylamide,N-(3-imidazolylpropyl)methacrylamide, N-(3-imidazolylpropyl)acrylamide,N-(2-imidazolylethyl)methacrylamide,N-(1,1-dimethyl-3-imidazoylpropyl)methacrylamide,N-(1,1-dimethyl-3-imidazoylpropyl)acrylamide,N-(3-benzoimidazolylpropyl)acrylamide, andN-(3-benzoimidazolylpropyl)methacrylamide.

Exemplary quaternary salts of the ionic monomers of Formula II include,but are not limited to, (meth)acrylamidoalkyltrimethylammonium salts(e.g., 3-methacrylamidopropyltrimethylammonium chloride and3-acrylamidopropyltrimethylammonium chloride) and(meth)acryloxyalkyltrimethylammonium salts (e.g.,2-acryloxyethyltrimethylammonium chloride,2-methacryloxyethyltrimethylammonium chloride,3-methacryloxy-2-hydroxypropyltrimethylammonium chloride,3-acryloxy-2-hydroxypropyltrimethylammonium chloride, and2-acryloxyethyltrimethylammonium methyl sulfate).

Other grafting monomers that can provide positively charged groups to anion exchange resin include the dialkylaminoalkylamine adducts ofalkenylazlactones (e.g., 2-(diethylamino)ethylamine, (2-aminoethyl)trimethylammonium chloride, and 3-(dimethylamino)propylamineadducts of vinyldimethylazlactone) and diallylamine monomers (e.g.,diallylammonium chloride and diallyldimethylammonium chloride).

As described in further detail below, functionalized substrates of thepresent invention may be prepared using one of the above-describedgrafting monomers or a mixture of two or more of the above-describedgrafting monomers to alter the surface properties of a porous basesubstrate. When two or more of the above-described grafting monomers areused to alter the surface properties of a porous base substrate, themonomers may be grafted onto the porous base substrate in a singlereaction step (i.e., the two or more grafting monomers are all presentupon exposure to an electron beam) or in sequential reaction steps(i.e., a first grafting monomer is present upon a first exposure to anelectron beam and a second grafting monomer is present upon a secondexposure to the electron beam).

3. Reactants Bonded to Functional Groups on Grafted Species

As discussed above, a functional group along the grafted speciesextending from the porous base substrate can be reacted with one or moreother reactants. That is, a functional group such as an ethylenicallyunsaturated group, epoxy group, azlactone group, or isocyanato group canreact with a monomer or nucleophilic compound to further modify thesurface of the functionalized substrate. Any monomer that can react withthe grafted species can be used. The nucleophilic compound, for example,can have groups that alter the hydrophilic or hydrophobic character ofthe functionalized substrate, that provide other desired functionalgroups, or that alter the ionic character of the functionalizedsubstrate.

In some embodiments, the grafted species can impart a hydrophiliccharacter to the functionalized substrate that contains a porous basesubstrate that has a hydrophobic character prior to surfacemodification. The hydrophilic character of the functionalized substratecan result from the reaction of the porous base substrate with thegrafting monomer upon exposure to an electron beam or can result fromreaction of the grafted species with other reactants. The graftedspecies often contains a hydrophilic group. Suitable groups capable ofimparting a hydrophilic character include, for example, polyalkyleneoxide groups, (meth)acryloly groups, ionic groups, and nucleophilicgroups such as hydroxy, amino groups, and carboxy groups.

B. Functionalized Substrate Properties and Structural Characteristics

The functionalized substrates of the present invention have a variety ofsurface properties and structural characteristics depending on a numberof factors including, but not limited to, the porous base substrate, themethod of forming the porous base substrate, the species grafted ontointerstitial and outer surfaces of the porous base substrate, anypost-grafting treatments (e.g., a heating step) administered to thefunctionalized substrate, and any post-grafting reactions (e.g.,reactions of the additional function group of the grafted species with acompound such as a nucleophilic compound or a compound with an ionicgroup). A number of properties and characteristics of the functionalizedsubstrate are described below.

1. Increased Pore Size

In some embodiments of the present invention, the functionalizedsubstrate has an average final pore size greater than an average initialpore size of the porous base substrate prior to a surface modificationstep (e.g., prior to attachment of the grafted species or reaction of afunctional group on the grafted species with another compound such as amonomer or nucleophilic compound). In one exemplary embodimentdemonstrating increased pore size, the functionalized substratecomprises (i) a porous base substrate (e.g., a microporous basesubstrate such as a microporous membrane) having interstitial and outersurfaces, wherein the porous base substrate has an average initial poresize prior to a grafting step; and (ii) grafted species extending fromthe interstitial and outer surfaces, wherein the functionalizedsubstrate has an average final pore size, and the average final poresize of the functionalized substrate is greater than the average initialpore size of the porous base substrate. In this embodiment, thefunctionalized substrate desirably comprises a porous base substratethat is microporous membrane.

The increase in pore size enables the functionalized substrates to havea different utility compared to the porous base substrate beforeaddition of the grafted species. For example, flux or flow rate throughthe functionalized substrate can be greater, which enables goodpermeability of the functionalized substrate while maintainingrelatively low operating pressures when the functionalized substrate isused in filtration applications. Further, the increased pore size of thefunctionalized substrate compared to the porous base substrate allowsthe application of an additional coating onto the interstitial and outersurfaces of the functionalized substrate while maintaining open poresthroughout the functionalized substrate. Such additional coatings may beused to add further functionality to the functionalized substrates.

In one desired embodiment, the functionalized substrate having increasedpore size comprises a TIPS microporous membrane such as a TIPS membraneformed from a polymeric material such as PVDF. Prior to the presentinvention, known TIPS membranes formed by known TIPS membrane formationprocesses resulted in membranes having an average pore size of less thanabout 1.0 microns. Using prior art methods, it can be difficult toprepare a TIPS membrane having a relatively uniform average pore size of1.0 microns or greater. The present invention, however, enablesmembranes formed via a TIPS process to have an average pore size greaterthan 1.0 microns, and in some embodiments up to about 1.2 microns orlarger.

The average initial pore size for a microporous membrane formed via aTIPS process often ranges from about 0.6 to about 0.9 microns. Theaverage initial pore size of these microporous membranes may beincreased in the present invention to an average final pore size rangingfrom about 0.7 to about 1.2 microns. In other words, the average initialpore size may be increased as much as about 0.1 microns (about 0.2microns, about 0.3 microns, about 0.4 microns, about 0.5 microns, oreven about 0.6 microns). The average initial pore size may be increasedas much as about 17%. For example, the average initial pore size may beincreased as much as about 20%, about 30%, about 40%, about 50%, about60%, or about 70%.

2. Increased Water Flux Rates

The functionalized substrates of the present invention desirably have awater flux rate that is greater than zero. Typically, the water fluxrate of the functionalized substrate is greater than the initial waterflux rate of the base porous base substrate prior to a grafting step. Insome embodiments, the water flux rate of the functionalized substrate ismuch greater, for example, as much as 2 times greater than the initialwater flux rate of the porous base substrate prior to a grafting step.

One method of measuring the water flux rate of a given functionalizedsubstrate or porous base substrate is to measure the amount of timenecessary for a quantity of water to flow through the functionalizedsubstrate or porous base substrate at a constant temperature andpressure. A decrease in the amount of time necessary for a quantity ofwater at a constant temperature and pressure to flow through a givenfunctionalized substrate compared to the corresponding porous basesubstrate prior to surface modification indicates an increase in thewater flux rate of the functionalized substrate.

In some embodiments, the functionalized substrates of the presentinvention can experience an increase in water flux rate of as much asabout 25 to about 100% compared to the water flux rate of the porousbase substrate prior to a grafting step (i.e., prior to surfacemodification). (For example, see Comparative Example 6 and Examples30-31 below.)

3. Wettability

The functionalized substrates of the present invention can exhibitvarious degrees of wettability upon exposure to various solutions orsolvents. Wettability can often be correlated to the hydrophilic orhydrophobic character of the functionalized substrate. Table 1 belowprovides data relating to the effect of a 20 hour exposure to NaOHsolutions (i.e., 0.25N and 1N NaOH solutions) on several functionalizedsubstrates and a porous base substrate. As used herein, the term“instant wet” or “instant wettability” refers to the penetration ofdroplets of water into a given substrate as soon as the water contactsthe substrate surface, typically within less than 1 second. For example,a surface wetting energy of about 72 dynes or larger usually results ininstant wetting. As used herein, the term “no instant wet” refers topenetration of droplets of water into a given substrate but not as soonas the water contacts the substrate surface. As used herein, the term“no wetting” refers to the lack of penetration of droplets of water intoa given substrate. For example, a surface wetting energy of about 60dynes or less usually results in no wetting.

TABLE 1 Sodium Hydroxide Exposure Test (“Instant Wettability” Test)SR-603 SR-603 PEG 400 PEG 400 SR-344 di- dimethacrylate PEG 400methacrylate 20 wt % on diacrylate 20 wt % on DURAPORE DURAPORE 10 wt %on TIPS “A” HVHP14250 HVLP14250 TIPS “A” membrane membrane (hydrophilic)membrane 40 kGy 40 kGy membrane 40 kGy 1N NaOH instant wet instant wetno instant wet no wetting 20 hours 0.25N instant wet instant wet instantwet instant wet NaOH 20 hours

Table 1 shows data for a functionalized substrates prepared using a PVDFmembrane as the porous base substrate. These porous base substrates wereeither a TIPS membrane (see description of TIPS “A” film in Examplesection) or a membrane commercially available from Millipore Corporation(Billerica, Mass.) under the trade designation DURAPORE and that washydrophobic as purchased. Polyethylene glycol (400) dimethacrylatemonomer (from a 20 wt % solution in methanol, Sartomer SR-603commercially available from Sartomer Company, Inc. (Exton, Pa.)) wasgrafted onto the porous base substrates upon exposure to an electronbeam at a dose of 40 kGy. The resulting functionalized substrates retaininstant wettability when exposed to a 0.25 N NaOH solution for 20 hoursor a 1 N NaOH solution for 20 hours.

For comparison, another DURAPORE membrane, which is hydrophilic aspurchased and that was not surface modified (this corresponds to ahydrophilic porous substrate), had instant wettability when exposed to a0.25 N NaOH solution for 20 hours but had no instant wettability whenexposed to a 1 N NaOH solution for 20 hours. Further, for comparison, afunctionalized substrate was prepared by exposing polyethylene glycol(400) diacrylate monomer (from a 10 wt % solution in methanol, SartomerSR-344 commercially available from Sartomer Company, Inc. (Exton, Pa.))and a microporous PVDF TIPS membrane to an electron beam at a dose of 40kGy. The resulting functionalized substrate retained instant wettabilitywhen exposed to a 0.25 N NaOH solution for 20 hours, but did not exhibitany wetting when exposed to a 1 N NaOH solution for 20 hours.

4. Resistance to Heat

The functionalized substrates also exhibit resistance to multipleexposures to heat. For example, Table 2 below provides data relating tothe effect of simple durability tests followed by multiple one hour ovenexposures to a temperature of 121° C. on an exemplary functionalizedsubstrate prepared by exposing a TIPS membrane and polyethylene glycol(400) dimethacrylate monomer (from a 20 wt % solution in methanol) to anelectron beam at a dose of 40 kGy.

TABLE 2 Heat and Caustic Exposure Test SR-603 PEG 400 DURAPORE ®dimethacrylate HVLP14250 40 kGy, 20 wt % on membrane without TIPS “A”membrane E-beam grafting Step Procedure Seconds: Seconds: — Initial FluxTime 18.2 15.1 (sec.) 1 100 ml IPA flush 18.1 15.2 2 1 hour 121° C. 14.514.5 3 16 hours 0.25 N wets wets NaOH soak 4 1 hour 121° C. 18.5 26.9 51 hour 121° C. 16.1 38.2 6 1 hour 121° C. 15.3 51.6 7 1 hour 121° C.16.0 61.4 8 1 hour 121° C. 15.3 96.4 9 1 hour 121° C. 14.5 108.9 10  1hour 121° C. 14.0 164.8 11  1 hour 121° C. 14.6 154.3

The water flux time is equal to the amount of time needed for 100 ml ofwater to pass through a 47 mm Gelman Sciences (now known as PallCorporation (Ann Arbor, Mich.)) 4238 disk holder at 533 mm Hg (21 inchesHg). As shown in Table 2, the functionalized substrate retained a waterflux time substantially equal to or less than an initial flux time aftermultiple heat cycles and exposure to a 0.25 N NaOH solution for 16hours. In comparison, the water flux time of an unmodified hydrophilicmicroporous PVDF DURAPORE® membrane exposed to the same series of stepsshowed a substantial increase in the water flux time (i.e., asubstantial decrease in the water flux rate through the substrate).

II. Method of Making Functionalized Substrates

The above-described functionalized substrates may be prepared using acombination of process steps. The method comprises the steps ofproviding a porous base substrate having interstitial and outersurfaces; imbibing the porous base substrate with a first solution toform an imbibed porous base substrate, the first solution comprising atleast one grafting monomer having (a) a free-radically polymerizablegroup and (b) an additional functional group comprising an ethylenicallyunsaturated group, an epoxy group, an azlactone group, an ionic group,an alkylene oxide group, or combination thereof; and exposing theimbibed porous base substrate to a controlled amount of electron beamradiation so as to form a first functionalized substrate comprisinggrafted species attached to the surfaces of the porous base substrate,wherein at least one of the grafted species comprises the additionalfunctional group. Some of the porous base substrates used in thisembodiment can be hydrophobic, microporous, or a combination thereof.

In one embodiment, the method comprises the steps of providing a porousbase substrate having interstitial and outer surfaces; imbibing theporous base substrate with a first solution to form an imbibed porousbase substrate, the first solution comprising at least one graftingmonomer having (a) a free-radically polymerizable group and (b) anadditional functional group comprising an ethylenically unsaturatedgroup, an epoxy group, an azlactone group, an ionic group, an alkyleneoxide group, or combination thereof; positioning the imbibed porous basesubstrate between a removable carrier layer and a removable cover layerto form a multilayer structure; exposing the multilayer structure to acontrolled amount of electron beam radiation so as to form afunctionalized substrate positioned between the removable carrier layerand the removable cover layer, the functionalized substrate comprisinggrafted species attached to the surfaces of the porous base substrate,wherein at least one of the grafted species comprises the additionalfunctional group; and removing the carrier layer and cover layers fromthe multilayer structure. Some of the porous base substrates used inthis embodiment can be hydrophobic, microporous, or a combinationthereof.

One exemplary method for making functionalized substrates is depicted inFIG. 1. As shown in FIG. 1, exemplary method 10 comprises the followingsteps: an imbibing step 100, a sandwiching step 200, an irradiation step300, a peeling step 400, a wash/rinse step 500, a drying step 600, and atake-up step 700. Each of these exemplary steps is described in furtherdetail below.

A. Exemplary Process Steps

Methods of making functionalized substrates of the present invention maycomprise one or more of the following steps.

1. Imbibing Step

As shown in FIG. 1, a roll 11 comprising a base porous base substrate 12may be unwound so that base porous base substrate 12 enters intoimbibing step 100. In imbibing step 100, base porous base substrate 12is brought into contact or into proximity with applicator 14 that isconnected to a reservoir of solution 13 containing one or more graftingmonomers. Rollers 15 and 16 guide base porous base substrate 12 pastapplicator 14 so that base porous base substrate 12 is exposed tosolution 13 for a desired amount of time. Typically, the exposure timeof the base porous base substrate 12 to solution 13 is up to about 1.0minutes, more typically, less than about 15 seconds. Base porous basesubstrate 12 usually proceeds through imbibing step 100 and toirradiation step 300 in less than 1 minute. In some imbibing steps, theporous base substrate 12 is saturated with the solution 13.

As discussed above, solution 13 may comprise one or more graftingmonomers suitable for grafting onto interstitial and outer surfaces ofbase porous base substrate 12. Any of the exemplary grafting monomersdescribed above can be included in solution 13. In addition to graftingmonomers, solution 13 can contain other materials such as, for example,solvents. The concentration of each grafting monomer in solution 13 mayvary depending on a number of factors including, but not limited to, thegrafting monomer or monomers in solution 13, the extent of graftingdesired, the reactivity of the grafting monomer(s), and the solventused. Typically, the concentration of each grafting monomer in solution13 ranges from about 1 wt % to about 100 wt %, desirably, from about 5wt % to about 30 wt %, and more desirably from about 10 wt % to about 20wt % based on a total weight of solution 13.

Once base porous base substrate 12 has been imbibed in solution 13 for adesired period of time, the base porous base substrate 12 is directedtoward sandwiching step 200 via guide roller 17. Guide roller 17 may beused to meter excess solution 13 from the imbibed base porous basesubstrate 12 if so desired. Alternately, rollers (not shown) could beused to squeeze air bubbles and excess solution 13 from the imbibed baseporous base substrate 12. Typically, base porous base substrate 12enters sandwiching step 200 in a substantially saturated condition(i.e., base porous base substrate 12 contains a maximum amount ofsolution 13 or close to a maximum amount) wherein substantially all ofthe interstitial and outer surfaces of base porous base substrate 12 arecoated with solution 13.

It should be noted that imbibing step 100 is only one possible method ofintroducing solution 13 into base porous base substrate 12. Othersuitable methods include, but are not limited to, a spray coatingmethod, flood coating method, knife coating, etc.

2. Sandwiching Step

In sandwiching step 200, imbibed base porous base substrate 12 issandwiched (i.e., positioned) between a removable carrier layer 22 and aremovable cover layer 19 to form multilayer sandwich structure 24. Asshown in exemplary method 10, removable cover layer 19 may be unwoundfrom roll 18 and brought into contact with an outer surface of imbibedbase porous base substrate 12 via roller 20, while removable carrierlayer 22 may be unwound from roll 21 and brought into contact with anopposite outer surface of imbibed base porous base substrate 12 viaroller 23.

Removable cover layer 19 and removable carrier layer 22 may comprise anyinert sheet material that is capable of providing temporary protectionto functionalized substrate 30 (i.e., grafted base porous base substrate12) from direct exposure to oxygen upon exiting chamber 25. Suitableinert sheet materials for forming removable cover layer 19 and removablecarrier layer 22 include, but are not limited to, polyethyleneterephthalate film material, other aromatic polymer film materials, andany other non-reactive polymer film material. Once assembled, multilayersandwich structure 24 proceeds to irradiation step 300.

3. Irradiation Step

In irradiation step 300, multilayer sandwich structure 24 is exposed toa sufficient quantity of radiation so as to graft one or more monomerswithin solution 13 onto interstitial and outer surfaces of base porousbase substrate 12 so as to form multilayer sandwich structure 27comprising functionalized substrate 30 sandwiched between removablecarrier layer 22 and removable cover layer 19. As shown in exemplarymethod 10, multilayer sandwich structure 24 proceeds through chamber 25,which contains at least one device 26 capable of providing a sufficientdose of radiation. A single device 26 is capable of providing asufficient dose of radiation, although two or more devices 26 may beused especially for relatively thick base porous base substrates 12.Typically, chamber 25 comprises an inert atmosphere such as nitrogen,carbon dioxide, helium, argon, etc. with a minimal amount of oxygen,which is known to inhibit free-radical polymerization. In embodimentswherein base porous base substrate 12 is irradiated without removablecover layer 19, the amount of oxygen within chamber 25 can be more of aconcern. When removable carrier layer 22 and removable cover layer 19cover the base porous base substrate 12, exposure to oxygen withinchamber 25 is minimal.

Although other sources of irradiation may be used, desirably device 26comprises an electron beam source. Electron beams (e-beams) aregenerally produced by applying high voltage to tungsten wire filamentsretained between a repeller plate and an extractor grid within a vacuumchamber maintained at about 10⁻⁶ Torr. The filaments are heated at highcurrent to produce electrons. The electrons are guided and acceleratedby the repeller plate and extractor grid towards a thin window of metalfoil. The accelerated electrons, traveling at speeds in excess of 10⁷meters/second (m/sec) and possessing about 150 to 300 kilo-electronvolts (keV), pass out of the vacuum chamber through the foil window andpenetrate whatever material is positioned immediately beyond the foilwindow.

The quantity of electrons generated is directly related to the extractorgrid voltage. As extractor grid voltage is increased, the quantities ofelectrons drawn from the tungsten wire filaments increase. E-beamprocessing can be extremely precise when under computer control, suchthat an exact dose and dose rate of electrons can be directed againstmultilayer sandwich structure 24.

Electron beam generators are commercially available from a variety ofsources, including the ESI “ELECTROCURE” EB SYSTEM from Energy Sciences,Inc. (Wilmington, Mass.), and the BROADBEAM EB PROCESSOR from PCTEngineered Systems, LLC (Davenport, Iowa). For any given piece ofequipment and irradiation sample location, the dosage delivered can bemeasured in accordance with ASTM E-1275 entitled “Practice for Use of aRadiochromic Film Dosimetry System.” By altering extractor grid voltage,beam diameter and/or distance to the source, various dose rates can beobtained.

The temperature within chamber 25 is desirably maintained at an ambienttemperature by conventional means. Without intending to be limited toany particular mechanism, it is believed that the exposure of theimbibed porous base substrate to an electron beam results in freeradical initiation on the substrate which can then react with monomershaving a double bond such as monomers having an ethylenicallyunsaturated group.

The total dose received by multilayer sandwich structure 24 primarilyaffects the extent to which the grafting monomer is grafted onto theporous base substrate. In general, it is desirable and typical toconvert at least 10 wt %, desirably 20 wt %, even more desirably greaterthan 50 wt % of the grafting monomers added during the imbibing step tografted species. Further, it is desirable and typical to graft as muchas about 5 wt %, desirably as much as about 10 wt %, more desirably asmuch as about 20 wt % (or as much as about 100 wt %) of one or moregrafting monomers added during the imbibing step onto base porous basesubstrate 12, based on a total weight of base porous base substrate 12.Dose is dependent upon a number of processing parameters, includingvoltage, speed and beam current. Dose can be conveniently regulated bycontrolling line speed (i.e., the speed with which multilayer sandwichstructure 24 passes under device 26), and the current supplied to theextractor grid. A target dose (e.g., 20 kGy) can be convenientlycalculated by multiplying an experimentally measured coefficient (amachine constant) by the beam current and dividing by the web speed todetermine the exposure. The machine constant varies as a function ofbeam voltage.

While the controlled amount of electron beam radiation exposure isdependent upon the residence time, as a general matter, the monomersimbibed on the porous base substrate 12 that is part of multilayersandwich structure 24 will generally be significantly grafted uponreceiving a controlled amount of dosage ranging from a minimum dosage ofabout 10 kilograys (kGy) to a maximum dosage of about 60 kGy. Typically,the total controlled amount of dosage ranges from about 20 kGy to about40 kGy. While low dose rates and longer residence times are preferredfor radiation grafting, practical operation may necessitate speeds thatforce higher dose rates and shorter residence. Exclusion of oxygen in amultilayer sandwich allows free radical chemistry to continue afterE-beam exposure for a duration sufficient to improve the grafting yield.

4. Peeling Step

Upon exiting chamber 25, multilayer sandwich structure 27 proceedstoward peeling step 400. In peeling step 400, multilayer sandwichstructure 27 is disassembled by separating removable carrier layer 22and removable cover layer 19 from functionalized substrate 30. As shownin exemplary method 10, removable cover layer 19 is separated from anouter surface of functionalized substrate 30 and taken-up as roll 28,while removable carrier layer 22 is separated from an opposite outersurface of functionalized substrate 30 and taken-up as roll 29.

In one desired embodiment, after exposure to an electron beam andexiting chamber 25, removable carrier layer 22 and removable cover layer19 are allowed to remain on functionalized substrate 30 for a period oftime prior to peeling step 400 so as to provide prolonged protection offunctionalized substrate 30 from exposure to oxygen. Desirably,removable carrier layer 22 and removable cover layer 19 remain onfunctionalized substrate 30 for at least 15 seconds, more desirably, forabout 30 to about 60 seconds after exiting chamber 25. However, there isno upper time limit that will reduce grafting quality and multilayersandwich structure 27 can remain intact for an extended time period aswould be the case if batch processing rolls of multilayer sandwichstructure 27 are prepared. Once multilayer sandwich structure 27 isdisassembled, functionalized substrate 30 can proceed to an optionalwashing/rinsing step 500.

5. Washing/Rinsing Step

In optional washing/rinsing step 500, functionalized substrate 30 iswashed or rinsed one or more times in rinse chamber 31 to remove anyunreacted monomers, solvent or other reaction by-products fromfunctionalized substrate 30. Typically, functionalized substrate 30 iswashed or rinsed up to three times using a water rinse, an alcoholrinse, a combination of water and alcohol rinses, and/or a solvent rinse(e.g., acetone, MEK, etc). When an alcohol rinse is used, the rinse mayinclude one or more alcohols including, but not limited to, isopropanol,methanol, ethanol, or any other alcohol that is practical to use and aneffective solvent for any residual monomer. In each rinse step,functionalized substrate 30 may pass through a rinse bath or a rinsespray.

6. Drying Step

In optional drying step 600, functionalized substrate 30 is dried toremove any rinse solution from functionalized substrate 30. Typically,functionalized substrate 30 is dried in oven 32 having a relatively lowoven temperature for a desired period of time (referred to herein as“oven dwell time”). Oven temperatures typically range from about 60° C.to about 120° C., while oven dwell times typically range from about 120to about 600 seconds.

Any conventional oven may be used in optional drying step 600 of thepresent invention. Suitable ovens include, but are not limited to, aconvection oven.

It should also be noted that in other embodiments drying step 600 canproceed before washing/rinsing step 500 eliminating volatile componentsbefore extraction of non-grafted residue.

7. Take-Up Step

Following optional drying step 600, dried functionalized substrate 30can be taken up in roll form as roll 33. Functionalized substrate 30 maybe stored for future use in roll form, used immediately as is, orfurther processed to further alter the surface properties offunctionalized substrate 30.

8. Further Processing

In one exemplary embodiment, functionalized substrate 30 is furtherprocessed to alter the surface properties of functionalized substrate30. In this embodiment, functionalized substrate 30 is processed througha grafting process such as exemplary method 10 for a second time (oreven more times) in order to (i) graft additional grafting monomers ontointerstitial and outer surfaces of functionalized substrate 30, (ii)graft additional monomers onto grafted species extending frominterstitial and outer surfaces of functionalized substrate 30, or (iii)both (i) and (ii). For example, in one exemplary embodiment,functionalized substrate 30 is prepared by imbibing a porous basesubstrate with a first solution comprising one or more grafting monomersin a solvent, wherein the one or more grafting monomers comprise atleast one grafting monomer having (a) a free-radically polymerizablegroup and (b) at least one additional functional group thereon (e.g., anethylenically unsaturated group, an epoxy group, an azlactone group, anisocyanato group, an ionic group, an alkylene oxide group, orcombination thereof); and then exposing the porous base substrateimbibed with the first solution to a controlled amount of electron beamradiation so as to graft the one or more grafting monomers tointerstitial and outer surfaces of the porous base substrate. Theresulting first functionalized substrate is rinsed to remove anyunreacted grafting monomer, and then subsequently imbibed with a secondsolution comprising one or more grafting monomers in a solvent, whereinthe one or more grafting monomers comprise at least one grafting monomerhaving (a) a free-radically polymerizable group and (b) at least oneadditional functional group thereof such as an ethylenically unsaturatedgroup, epoxy group, azlactone group, isocyanato group, ionic group, analkylene oxide group, or combination thereof; and then exposing thefirst functionalized substrate imbibed with the second solution to acontrolled amount of electron beam radiation to form a secondfunctionalized substrate. The further modified functionalized substrate30 can then proceed through an optional washing/rinsing step, such asexemplary washing/rinsing step 500 in exemplary method 10, and anoptional drying step, such as exemplary drying step 600 in exemplarymethod 10.

In a further exemplary embodiment, functionalized substrate 30 isfurther processed (e.g., after a single pass or numerous passes througha grafting process such as exemplary method 10) to further alter thesurface properties of functionalized substrate 30 by passingfunctionalized substrate 30 through a process such as shown in exemplarymethod 50 in FIG. 2. In this embodiment, functionalized substrate 30 isbrought into contact with a solution containing one or more reactantsthat can react with functional groups along grafted species offunctionalized substrate 30. Although FIG. 2 shows the functionalizedsubstrate 30 provided from roll 33, the process steps depicted in FIG. 2can be performed in a continuous process with the process steps depictedin FIG. 1.

As shown in FIG. 2, exemplary method 50 starts by removingfunctionalized substrate 30 from roll 33, and guiding functionalizedsubstrate 30 into imbibing step 100. In imbibing step 100,functionalized substrate 30 is brought into contact with a solution 13containing one or more reactants. The reactants may be compounds thatreact with or interact with one or more functional groups (e.g., epoxygroups, ethylenically unsaturated groups, azlactone group, isocyanatogroups, or ionic groups, alkylene oxide groups, or a combinationthereof) along the grafted species of functionalized substrate 30. Forexample, a compound having a nucleophilic group can react with anazlactone group, isocyanato group, or epoxy group or a compound having acharged group can interact with an ionic group. Rollers 15 and 16 guidefunctionalized substrate 30 through solution 13 so that functionalizedsubstrate 30 is in contact with solution 13 for a desired amount oftime. Typically, the dwell time of functionalized substrate 30 insolution 13 is less than about 1.0 minutes.

The concentration of each reactant in solution 13 may vary depending ona number of factors including, but not limited to, the reactant orreactants in solution 13, the extent of surface modification desired,and the solvent used. Typically, the concentration of each reactant insolution 13 ranges from about 5 wt % to about 100 wt % based on a totalweight of solution 13.

Once functionalized substrate 30 has been imbibed with solution 13 for adesired period of time, functionalized substrate 30 is directed towardan optional heating step 800 via guide roller 17. Guide roller 17 may beused to meter excess solution 13 from functionalized substrate 30 if sodesired. Typically, functionalized substrate 30 enters optional heatingstep 800 in a substantially saturated condition (i.e., functionalizedsubstrate 30 contains a maximum amount of solution 13 or close to amaximum amount).

Although not shown in FIG. 2, exemplary method 50 can include anoptional step wherein functionalized substrate 30 imbibed with solution13 is sandwiched between removable materials, such as removable carrierlayer and removable cover layer comprising a non-reactive polymer film,such as PET, in order to prevent evaporation of chemicals and/or solventcarrier during heating step 800. The same removable materials describedabove can be used in this step. Use of removable covers can, at least insome embodiments, minimize VOC emissions and reduce flammabilityconcerns. In this embodiment, a peeling step similar to peeling step 400may follow heating step 800.

9. Heating Step

In optional heating step 800, functionalized substrate 30 is heated tofacilitate the reaction between reactants added during the imbibing step100 and one or more functional groups along grafted species offunctionalized substrate 30 so as to produce further functionalizedsubstrate 35. Typically, during the optional heating step 800,functionalized substrate 30 is subjected to an oven 36 having an oventemperature of up to about 120° C. depending on a number of factorsincluding, but not limited to, the reactants, the base porous basesubstrate, the functional groups present on the grafted species, and thedwell time within oven 36. Typically, the oven temperature used inoptional heating step 800 is 30° C. of greater (desirably, 40° C. orgreater, 50° C. or greater, or 60° C. or greater). The oven temperaturetypically ranges from about 60° C. to about 120° C. Typically, ovendwell time in optional heating step 800 ranges from about 60 seconds toabout 1 hour.

Any conventional oven may be used in the optional heating step of thepresent invention, such as optional heating step 800 of exemplary method50. Suitable ovens include, but are not limited to, the above-describedovens used in optional drying step 600 of exemplary method 10.Desirably, the oven used in optional heating step 800 of exemplarymethod 50 comprises a circulating air oven.

Once further functionalized substrate 35 exits oven 36, functionalizedsubstrate 35 may pass through an optional washing/rinsing step 500 andan optional drying step 600 as described above. Following optionaldrying step 600, dried functionalized substrate 35 can be taken up inroll form as roll 37. Further functionalized substrate 35 may be storedfor future use in roll form, used immediately as is, or furtherprocessed in one or more additional process steps (not shown). Suitableadditional process steps may include, but are not limited to, a reactionstep or a coating step wherein a coating composition is applied tofurther functionalized substrate 35, a lamination step wherein one ormore additional layers are temporarily or permanently joined to furtherfunctionalized substrate 35, an assembling step wherein furtherfunctionalized substrate 35 is combined with one or more additionalcomponents to form a finished product (e.g., a filter assembly), apackaging step wherein further functionalized substrate 35 or a finishedproduct comprising further functionalized substrate 35 is packagedwithin a desired packaging material (e.g., a polyethylene film or bag),or any combination thereof.

B. Process Parameters

The methods of making functionalized substrates of the present inventionmay also be described by one or more process parameters including, butnot limited to, the process parameters provided below.

1. Batch Versus Continuous Process

It should be noted that the methods of making functionalized substratesof the present invention may be performed using a continuous process,such as exemplary method 10 shown in FIG. 1, or alternatively, using abatch process wherein one or more of the above-described process stepsare performed separate from one another. Desirably, the methods ofmaking functionalized substrates are performed using a continuousprocess, such as exemplary method 10 shown in FIG. 1.

2. Line Tension

When using a continuous process, such as exemplary method 10, one ormore drive rolls (not shown) may be used to move base porous basesubstrate 12 or functionalized substrate 30 through the continuousprocess. The one or more drive rolls provide sufficient tension on baseporous base substrate 12 and functionalized substrate 30 to move baseporous base substrate 12 and functionalized substrate 30 through a givenapparatus. Care should be taken when determining the amount of tensionto apply in order to prevent shrinkage and/or tearing of base porousbase substrate 12 or functionalized substrate 30 during processing. If astronger carrier web (e.g., removable carrier layer 22) is used toconvey base porous base substrate 12 or functionalized substrate 30,then the tension load is easier to adjust without transmitting thetension load through the substrate itself.

In the exemplary continuous grafting process of the present invention,the one or more drive rolls typically operate in a range of 5 to 40 lbs(22 to 178 Newtons) of tension on a (12 inch) 30 cm wide web of baseporous base substrate 12 or functionalized substrate 30 in order to movebase porous base substrate 12 or functionalized substrate 30 through agiven apparatus, resulting in a tension of 0.7 to 5.9 Newtons per linealcentimeter of base porous base substrate 12 or functionalized substrate30. In one desired embodiment, the one or more drive rolls operate in arange of 1.4 to 3.0 Newtons per lineal centimeter of base porous basesubstrate 12 or functionalized substrate 30.

3. Line Speed

In the exemplary continuous grafting process of the present invention,the one or more drive rolls also provide a desired line speed through agiven apparatus. Desirably, base porous base substrate 12 andfunctionalized substrate 30 move through a given apparatus at a linespeed of at least about 1.52 meters/minute (mpm) (5 fpm). In one desiredembodiment, base porous base substrate 12 and functionalized substrate30 move through a given apparatus at a line speed ranging from about3.05 mpm (10 fpm) to about 30.5 mpm (100 fpm).

C. Altered Properties of the Functionalized Substrates

The disclosed methods of making functionalized substrate may be used toprepare a variety of functionalized substrates. The functionalizedsubstrates have at least one group selected from (i) an ethylenicallyunsaturated group, (ii) an epoxy group or a ring-opened epoxy linkagegroup, (iii) an azlactone group or a ring-opened azlactone linkagegroup, (iv) an isocyanato group, urethane linkage group, or urea linkagegroup, (v) an ionic group, (vi) an alkylene oxide group, or anycombination of (i) to (vi). In some embodiments, the method of making afunctionalized substrate can alter the properties of the porous basesubstrate.

In any of the above-described methods of making a functionalizedsubstrate, any of the above-mentioned base porous base substrates,grafting monomers, and reactants may be used to form a givenfunctionalized substrate. The base porous base substrate is often in theform of a porous membrane such as a microporous membrane, a nonwovenweb, or porous fibers. In some embodiment, the base porous basesubstrate comprises a hydrophobic microporous membrane formed by athermally-induced phase separation (TIPS) method.

1. Increased Average Pore Size

In some methods, the average pore size can be altered. The methodcomprises the steps of providing a porous base substrate having anaverage initial pore size; imbibing the porous base substrate with afirst solution comprising at least one grafting monomer having (a) afree-radically polymerizable group and (b) at least one additionalfunctional group thereon; exposing the porous base substrate to acontrolled amount of electron beam radiation so as to graft the one ormore grafting monomers to interstitial and outer surfaces of the porousbase substrate; and exposing the grafted porous base substrate to a heatcycle at 30° C. or greater (desirably, 60° C. or greater), wherein themethod results in a functionalized substrate having an average finalpore size, wherein the average final pore size of the functionalizedsubstrate is greater than the average initial pore size of the porousbase substrate. In this embodiment, the porous base substrate is often amicroporous membrane. For example, the microporous membrane can behydrophobic microporous membrane such as a TIPS membrane.

In some of the above-described methods of increasing pore size, theaverage initial pore size of the microporous base substrate (prior to agrafting step) typically ranges from about 0.6 to about 0.9 microns,while the average final pore size of the grafted microporous basesubstrate typically ranges from about 0.7 to about 1.2 microns. Suchincreases in average pore size are particularly noticeable when themicroporous membrane comprises a hydrophobic microporous membrane, andespecially a hydrophobic microporous membrane formed by athermally-induced phase separation (TIPS) method. For example, themicroporous membrane can comprise PVDF that is prepared using the TIPSmethod.

The average pore size can be increased, for example, when a graftingmonomer is used that has two free-radically polymerizable groups.Although not wishing to be bound by theory, the grafting of both ofthese groups to the porous base substrate may result in a stress on thesurfaces of the substrate resulting in an increased pore size. Thegrafting monomer is often selected to provide a hydrophilic group. Forexample, the grafting monomer can be a polyalkylene glycoldi(meth)acrylate.

In another example, the average pore size can also be increased byreacting a nucleophilic compound having a plurality of nucleophilicgroups with functional groups on more than one grafted species resultingin the crosslinking of the grafted species. Although not wishing to bebound by theory, the crosslinking of the grafted species may result instress on the surfaces of the substrate resulting in an increased poresize. The nucleophilic compound is often selected to provide ahydrophilic group. For example, a polyalkylene glycol diamine orpolyalkylene glycol triamine can be used as the nucleophilic compound.

In yet other examples, the average pore size also can be increased usinga combination of different types of grafting monomers. A first graftingmonomer can include two free-radically polymerizable groups and a secondgrafting monomer can include a functional group that is an epoxy group,azlactone group, isocyanato group, or combination thereof. The secondgrafting monomer can then be reacted with a nucleophilic compound havinga plurality of nucleophilic groups. The nucleophilic compound can reactwith more than one epoxy group, azlactone group, isocyanato group, orcombinations thereof resulting in the crosslinking of multiple graftedspecies. The first and second grafting monomers can be included in thesame imbibing solution and grafted at the same time or can be includedin separate imbibing solutions and grafted in a sequential manner. Theorder of grafting of the monomers typically is not critical. At leastone of the grafting monomers or the nucleophilic compound is oftenchosen to provide a hydrophilic group.

2. Hydrophilic/Hydrophobic Character

In other embodiments, the method of making a functionalized substratealters the hydrophobic nature of the porous base substrate. For example,the grafted species can include a hydrophilic group. In other examples,the grafted species without a hydrophilic group can be reacted with anucleophilic compound that contains a hydrophilic group. In still otherexamples, a first grafted species can include hydrophilic group and asecond grafted species without a hydrophilic group can be reacted with anucleophilic compound that contains a hydrophilic group.

In some methods of making a functionalized substrate, the graftingmonomer contains two free-radically polymerizable groups as well as ahydrophilic group. For example, alkylene glycol di(meth)acrylates can beused as grafting monomers to impart a hydrophilic character to ahydrophobic porous base substrate. These grafting monomers have two(meth)acryl groups and a hydrophilic polyalkylene glycol (i.e.,polyalkylene oxide) group. These same grafting monomers can be used toincrease the average pore size of microporous membranes such as TIPSmembranes.

When the functionalized substrate has grafted species that contains anepoxy group, an azlactone group, or an isocyanato group, thefunctionalized substrate can be further treated to react thesefunctional groups with a nucleophilic compound having a plurality ofnucleophilic groups to impart a hydrophilic character to a hydrophobicporous base substrate. Any unreacted nucleophilic groups will tend tocontribute to a hydrophilic functionalized substrate. Some exemplarynucleophilic compounds contain a hydrophilic group such as apolyalkylene oxide group in addition to the nucleophilic group. Forexample, the nucleophilic compound such as polyalkylene glycol diaminesand polyalkylene glycol triamines can include a plurality of aminogroups.

The present invention enables the formation of functionalized substrateshaving many of the advantages of a hydrophobic porous bases substrate(e.g., a hydrophobic microporous membrane), but with permanenthydrophilicity on the surfaces of the functionalized substrate. Thepresent invention eliminates many of the known problems associated withporous bases substrates formed from hydrophilic polymers including, butnot limited to, hygroexpansive issues; brittleness withouthumidification problems; mechanical strength weakness; and poor solvent,caustic and/or acidic resistance.

The present invention also enables the formation of functionalizedsubstrates having various degrees of hydrophilicity depending on thematerials and steps used to form a given functionalized substrate. Forexample, a hydrophobic porous membrane may be made hydrophilic, and thensubsequently treated to graft epoxy groups onto the hydrophilic porousmembrane. The resulting hydrophilic porous membrane remains hydrophiliceven though hydrophobic groups (e.g., epoxy groups) have been graftedthereon. The resulting hydrophilic porous membrane remains hydrophilic,and yet becomes more reactive due to the presence of epoxy groupsthereon.

The present invention is described above and further illustrated belowby way of examples, which are not to be construed in any way as imposinglimitations upon the scope of the invention. On the contrary, it is tobe clearly understood that resort may be had to various otherembodiments, modifications, and equivalents thereof which, after readingthe description herein, may suggest themselves to those skilled in theart without departing from the spirit of the present invention and/orthe scope of the appended claims.

EXAMPLES

Unless otherwise noted, all solvents and reagents were or can beobtained from Sigma-Aldrich Corp., St. Louis, Mo.

“TIPS “A” film” refers to a microporous poly(vinylidene fluoride) filmhaving a thickness of approximately 0.051 millimeters (0.002 inch), aGurley air flow value of approximately 7 seconds per 50 cubiccentimeters of air, and an average pore size of approximately 0.7micrometers. This film was produced as described in WO2005035641 withthe following specifics. PVDF polymer pellets (SOLEF 1012, SolvaySolexis Co., Thorofare, N.J.) were introduced into the hopper of a 40 mmco-rotating twin-screw extruder at 5.8 kg/hr. The nucleating agent,Pigment Blue 60 (PB60, Chromophtal Blue A3R, Ciba Specialty Chemicals,Basel, Switzerland) in powder form, was premixed with the diluent,glyceryl triacetate (TRIACETIN, Eastman Chemical Co., Kingsport, Tenn.),so that the final concentration of nucleating agent was 0.25 wt %. Thisblend was fed into an injection port located in the fourth zone of aneight-zone 40 mm twin screw extruder and melt mixed with the PVDF toform a homogeneous solution where the overall blend ratio was42.0/57.75/0.25, PVDF/TRIACETIN/PB 60. The twin screw extruder wasoperated at 150 RPM and at a decreasing temperature profile of 215° C.(zone 1) to 188° C. (zone 8). The melt was pumped through adouble-chromed coat-hanger slot film die and cast onto a patternedchrome roll that was maintained at 52° C. to form a cast film at 4.1meters/min. The film was fed continuously into a seven-tank water washbath where the TRIACETIN was removed. The film was then fed continuouslyinto a five-roll, machine-direction stretching device maintained at anincreasing temperature profile of 60° C. to 82° C. and at a stretchratio of approximately 1.7:1. The length stretched film was then fedcontinuously into an eight-zone, transverse-direction stretching devicemaintained at an increasing temperature profile of 99° C. to 132° C. anda stretch ratio of approximately 2.2:1. The film was slit to its finalwidth and wound onto a core. The film was approximately 50 microns inthickness, had a Gurley air flow value of about 7 sec/50 cm³ air, andhad an average pore size of about 0.7 microns.

“TIPS “B” film” refers to a microporous poly(vinylidene fluoride) filmhaving an average pore size of approximately 0.15 micrometers. TIPS “B”film was prepared using a method similar to that used to prepare TIPS Afilm.

“TIPS “C” film” refers to a microporous poly(propylene) film having anaverage pore size of approximately 0.6 micrometers. TIPS “C” film wasprepared according to the methods of U.S. Pat. Nos. 4,726,989 and5,120,594, each of which is assigned to 3M Company, St. Paul, Minn., andeach of which is hereby incorporated by reference in its entirety.

“TIPS “D” film” refers to a microporous poly(ethylene) film having anaverage pore size of approximately 0.6 micrometers. TIPS “D” film wasprepared according to the methods of U.S. Pat. Nos. 4,726,989 and5,120,594, each of which is assigned to 3M Company, St. Paul, Minn., andeach of which is hereby incorporated by reference in its entirety.

“EVOH film” refers to a microporous poly(vinyl alcohol-co-ethylene) filmof 68 mole percent vinyl alcohol and 32 mole percent ethylene preparedaccording to U.S. Pat. No. 5,962,544, which is assigned to 3M Company,St. Paul, Minn. and is hereby incorporated by reference.

“MEK” refers to methyl ethyl ketone.

“GMA” refers to glycidyl methacrylate.

“PVDF” refers to poly(vinylidene fluoride).

“JEFFAMINE XTJ-504” refers to JEFFAMINE XTJ-504, a polyether diamineavailable from Huntsman Corp., Houston, Tex.

“JEFFAMINE T-5000” refers to JEFFAMINE T-5000, a polyether triamineavailable from Huntsman Corp., Houston, Tex.

“DETA” refers to diethylenetriamine

“SR344” refers to a polyethylene glycol diacrylate with an averagemolecular weight of about 400 g/mole that was obtained from SartomerCo., Inc., Exton, Pa.

“SR603” refers to a polyethylene glycol dimethacrylate with an averagemolecular weight of about 400 g/mole that was obtained from SartomerCo., Inc., Exton, Pa.

“CD553” refers to a polyethylene glycol acrylate obtained from SartomerCo., Inc., Exton, Pa.

“APTAC” refers to 3-acrylamidopropyltrimethylammonium chloride.

“AMPS” refers to sodium 2-acrylamido-2-methyl-1-propanesulfonate.

“AETAC” refers to [2-(acryloyloxy)ethyl]trimethylammonium chloride.

“DURAPORE “A” film” refers to a hydrophilic film available under thetrade designation DURAPORE HVLP 14250 from Millipore Corp., Billerica,Mass.

“DURAPORE “B” film” refers to a hydrophobic film available under thetrade designation DURAPORE HVHP 14250 from Millipore Corp., Billerica,Mass.

“PEG” refers to polyethylene glycol.

“PES “A” film” refers to a MILIPORE EXPRESS MEMBRANE GPWP1polyethersulfone membrane, available from Millipore Corp., Billerica,Mass.

“PES “B” film” refers to SUPOR200 polyethersulfone membrane, availablefrom Pall Corp., East Hills, N.Y.

“NYLAFLO film” refers to a hydrophilic NYLON membrane having a pore sizerating of 0.45 micrometers, available from Pall Corp., East Hills, N.Y.

Electron Beam Processing

Electron beam irradiation was carried out using a Model CB-300 electronbeam system, obtained from Energy Sciences, Inc., Wilmington, Mass. Thefilm samples were placed between two sheets of poly(ethyleneterephthalate) film for the irradiation. The following procedure wasused unless otherwise specified. Samples of film were placed between twolarger area size pieces of 3-mil thick PET and taped together at oneend. This sandwich was then opened and the sample film was wetted withmonomer solution and the sandwich re-closed. Trapped air bubbles wereremoved and excess liquid was squeezed out by gently applying a rubberroller over the surface of the sandwich. The sandwich was taped to amoving web of PET and conveyed through the electron beam processor at aspeed of 6.1 meters per minute (mpm) (20 fpm) and at a voltage of 300keV with sufficient beam current applied to the cathode to deliver thetargeted dose. The beam was calibrated using thin film dosimeters,calibrated and traceable to a national standards laboratory (RISO,Denmark). In some cases, to lower the overall dose rate and increaseresidence time while under the beam, the dose was fractionated bymultiple passes through the beam to simulate a longer exposure time morecharacteristic of electron beams with cathodes extended in the webdirection (i.e. BroadBeam, etc).

After the sample passed through the beam, the sandwich was removed fromthe web and allowed to sit for a minute or more before being opened, thesample removed and allowed to soak in a tray of water. The water in thetray was changed three times. The sample was then blotted with papertowels and allowed to air dry. Residual monomers not easily removed withwater were extracted by washing with MEK, alcohol or other suitablesolvent as specified in the examples.

Water Flux Test

Water flux was determined by placing a disk of the test film having adiameter of approximately 47 millimeters (mm) (1.85 inches) in a Model4238 Pall Gelman magnetic filter holder (available from Pall Corp., EastHills, N.Y.). The filter holder was then placed on a filter flask thatwas attached to a vacuum pump. A vacuum gauge was used to monitor thevacuum. Approximately 150 milliliters (ml) of water was placed in thefilter holder and then vacuum was applied. After approximately 50 ml ofwater passed through the film (the vacuum gauge at this time indicatedapproximately 533 mm of mercury (approximately 21 inches of mercury),timing was commenced using a stopwatch. When all of the remaining waterhad passed through the film, timing was stopped. The water flux was thetime, measured in seconds, that elapsed for 100 ml of water to passthrough the membrane under a vacuum of 0.83 mm of mercury.

Average Pore Diameter

The average pore diameter was determined by allowing a wetting liquid tospontaneously fill the pores in the sample membrane and then using anon-reacting gas to displace the liquid from the pores of the membrane.The gas pressure and flow rates are accurately measured using anAutomated Capillary Flow Porometer, model number APP-1200-AEX withsupplied software, Capwin version 6.71.54 from Porous Materials Inc.(PMI) of Ithaca N.Y. Fluorinert FC-43, available from 3M, was used asthe wetting fluid and compressed nitrogen gas was used for displacementwith a maximum pressure setting of 689.5 kilonewtons/m² (kN/m²) (100psi). The tests were run in the wet up/dry down software configuration.

Preparative Example 1 Preparation of PVDF Non-Woven Film

A melt-blown PVDF microfiber nonwoven web was prepared using a methodand equipment similar to that described in Van A. Wente, “SuperfineThermoplastic Fibers,” Industrial Engineering Chemistry, vol. 48, pp.1342-1346 (August, 1956) and Van A. Wente et al., “Manufacture of SuperFine Organic Fibers”, Report No. 4364 of the Naval ResearchLaboratories, published May 25, 1954.

PVDF polymer pellets (SOLEF 1012, Solvay Solexis Co., Thorofare, N.J.)were used to produce meltblown webs utilizing a melt temperature of 234°C. and a mass flow rate of 0.35 g/hole/minute. Hot air, delivered at arate equivalent to 4.5 cubic meters of air at 0° C. at 101.3 kN/m² (1atmosphere) per meter of die face per minute and heated to 360 degreesC., was used to attenuate the fibers. The fibers were collected 15centimeters (cm) from the die face utilizing a perforated drum collectorto produce a web. The sample produced had an effective fiber diameter of12.3 microns (μm). The web had a basis weight of about 50 grams persquare meter (gsm) and a thickness of 0.13 cm. The effective fiberdiameter was calculated according to the method set forth in Davies, C.N., “The Separation of Airborne Dust and Particles,” Institution ofMechanical Engineers, London, Proceedings 1B, 1952.

Preparative Example 2 Preparation of EVOH Non-Woven Film

A melt-blown EVOH microfiber nonwoven web was prepared using the methodand equipment described in Preparative Example 1. EVOH polymer pellets(Poval C109B, Kuraray America Inc., 600 Lexington Ave., New York, N.Y.)were used to produce meltblown webs utilizing a melt temperature of 240°C. and a mass flow rate of 0.35 g/hole/minute. Hot air, delivered at arate equivalent to 4.5 cubic meters of air at 0° C. at 101.3 kN/m² (1atmosphere) per meter of die face per minute and heated to 285° C., wasused to attenuate the fibers. The fibers were collected 17 cm from thedie face utilizing a perforated drum collector to produce a web. Thesample produced had an effective fiber diameter of 35 μm. The web had abasis weight of about 150 gsm and a thickness of 0.21 cm. The web wasthen calendered between two 25 cm diameter smooth chrome steel rolls(70° C.) running at 1.5 mpm with a nip pressure between the rolls of 18kilograms-force per lineal centimeter. The resulting thickness of theweb was 0.05 cm.

Comparative Example 1

A sample of TIPS “A” film was saturated with JEFFAMINE XTJ-504 and wasthen placed in a glass vial and capped. The vial was then heated to atemperature of 60° C. for one hour. The vial was allowed to cool to roomtemperature, after which time the film sample was removed and was rinsedtwice with methanol. The rinsed film sample was allowed to dry at roomtemperature. When a drop of water was placed on the film sample, thedrop was observed not to be absorbed by the film.

Example 1-3

Three samples of TIPS “A” film each were weighed and were then saturatedwith a 20 weight percent solution of GMA in methanol and each wereirradiated with an electron beam dose of 40 kilograys (kGy). The sampleswere then extracted with MEK and were allowed to dry at roomtemperature. Each sample was then weighed again. The films of Examples1-3 were found to have increased in weight by 18.6%, 19.0%, and 20.5%,respectively. None of these samples were water absorbent. Each of thethree films was then saturated with JEFFAMINE XTJ-504 and each film wasthen placed in a glass vial and capped. The three vials containing thefilms were heated to a temperature of 60° C. for one hour. The vialswere allowed to cool to room temperature, after which time the filmsamples were removed and were rinsed twice with methanol. The rinsedfilm samples were then allowed to dry at room temperature and were againweighed. The film samples of Examples 1-3 were found to have increasedin weight by about 12%. Each film sample was changed from blue to greyafter the treatment. When drops of water were placed on each of the filmsamples, the drops were observed to be rapidly (e.g., nearly instantly)absorbed by the film samples.

Example 4

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy) as previously described. The film samplewas then saturated with a 20 weight percent solution of GMA in methanoland was again irradiated with an electron beam dose of 20 kilograys(kGy). The sample was then extracted with MEK and then with water andwas allowed to dry at room temperature. A portion of the sample was thensaturated with JEFFAMINE XTJ-504 and the film was then placed in a glassvial and capped. The vial containing the film was heated to atemperature of 60° C. for 45 minutes. The vial was allowed to cool toroom temperature, after which time the film sample was removed and wasrinsed twice with methanol. The rinsed film sample was then allowed todry at room temperature. The average pore size of the film sample wasevaluated as described above and was found to be larger than that of thestarting TIPS “A” film.

Example 5

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy) as previously described. This sampleportion was evaluated as described above and the average pore size wasfound to be centered at approximately 0.9 micrometers The film samplewas then saturated with a 20 weight percent solution of GMA in methanoland was irradiated with an electron beam dose of 40 kilograys (kGy). Thesample was then extracted with MEK and then with water and was allowedto dry at room temperature. A portion of the sample was then saturatedwith JEFFAMINE XTJ-504 and the film was then placed in a glass vial andcapped. The vial containing the saturated film was heated to atemperature of 60° C. for 45 minutes. The vial was allowed to cool toroom temperature, after which time the film sample was removed and wasrinsed twice with methanol. The average pore size of theJEFFAMINE-treated portion was 1.1 microns and the water flux of thesample was then measured as described above and was found to be 16.1seconds.

Example 6

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR603 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). This made the film hydrophilic. Thefilm sample was then saturated with a 10 weight percent solution of GMAin methanol and was irradiated with an electron beam dose of 40kilograys (kGy). The sample was then extracted with MEK and was allowedto dry at room temperature. The sample remained hydrophilic and was thensaturated with JEFFAMINE XTJ-504 and the film was then placed in a glassvial and capped. The vial containing the film was heated to atemperature of 60° C. for 45 minutes. The vial was allowed to cool toroom temperature, after which time the film sample was removed and wasrinsed twice with methanol. The average pore size of the film sample wasevaluated as described above and was found to be larger than that of thestarting TIPS “A” film. Portions of this film were found to rapidly(i.e., nearly instantly) absorb drops of water that were placed on thesurface of the film.

Example 7

A sample of TIPS “A” film was saturated with a methanol solution thatcontained 20 weight percent each SR603 and GMA. The film was thenirradiated with an electron beam dose of 40 kilograys (kGy). The samplewas then extracted with MEK and was allowed to dry at room temperature.A portion of the sample was then saturated with JEFFAMINE XTJ-504 andthe film was then placed in a glass vial and capped. The vial containingthe film was heated to a temperature of 60° C. for 45 minutes. The vialwas allowed to cool to room temperature, after which time the filmsample was removed and was rinsed twice with methanol. The average poresize of the film sample was evaluated as described above and was foundto be larger than that of the starting TIPS “A” film. This film wasfound to rapidly (i.e., nearly instantly) absorb drops of water thatwere placed on the surface of the film.

Example 8

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then rinsed with MEK andwas then allowed to dry at room temperature. A portion of the sample wasthen saturated with JEFFAMINE XTJ-504 and the film was then placed in aglass vial and capped. The vial containing the film was heated to atemperature of 60° C. for 45 minutes. The vial was allowed to cool toroom temperature, after which time the film sample was removed and wasrinsed twice with methanol. The average pore size of the film sample wasevaluated as described above and was found to be centered atapproximately 0.8 micrometers.

Comparative Examples 2-4

The average pore sizes of sets of samples of TIPS “A” film wasdetermined as described above. One set of samples (Comparative Example2) was irradiated with an electron beam dose of 40 kilograys (kGy), oneset of samples (Comparative Example 3) was irradiated with an electronbeam dose of 100 kilograys (kGy), and one set of samples (ComparativeExample 4) was saturated with methanol and was irradiated with anelectron beam dose of 40 kilograys (kGy). The average pore sizes of theirradiated samples were then determined and were found to be essentiallyequivalent to those of the samples before they were irradiated.

Comparative Example 5

The average pore size of a sample of TIPS “A” film was determined asdescribed above. The sample was then heated to 120° C. in an oven. Afterthe sample was allowed to cool to room temperature, the average poresize of the sample was then determined and was found to be essentiallyequivalent to that of the sample before it was heated.

Examples 9-11

Three samples of TIPS “A” film were saturated with a 10 weight percentsolution of SR344 in methanol. One of the samples was then irradiatedwith an electron beam at a dose of 20 kilograys (kGy) (Example 9), oneof the samples was irradiated at a dose of 40 kGy (Example 10), and oneof the samples was irradiated at a dose of 60 kGy (Example 11). Eachsample was then rinsed three times with water and each was placed inwater that was heated to 70° C. for one hour. Each sample was observedto be readily wetted by the water. The average pore sizes of theirradiated samples were then determined and were found to be greaterthan that of TIPS “A” film that had not been irradiated.

Examples 12-14

Three samples of TIPS “A” film were saturated with a 25 weight percentsolution of SR603 in methanol. One of the samples was then irradiatedwith an electron beam at a dose of 20 kilograys (kGy) (Example 12), oneof the samples was irradiated at a dose of 40 kGy (Example 13), and oneof the samples was irradiated at a dose of 60 kGy (Example 14). Eachsample was then rinsed three times with water and then each was placedin water that was heated to 70° C. for one hour. Each sample wasobserved to be readily wetted by the water. The average pore sizes ofthe irradiated samples were then determined and were found to be greaterthan that of TIPS “A” film that had not been irradiated.

Example 15

The average pore size and water flux of a sample of each of DURAPORE “A”film and DURAPORE “B” film was determined. A sample of DURAPORE “B” filmwas saturated with a 20 weight percent solution of GMA in methanol andwas irradiated with an electron beam dose of 40 kilograys (kGy). Thesample was then extracted with MEK and was allowed to dry at roomtemperature. The film was then saturated with JEFFAMINE XTJ-504 and thefilm was then placed in a glass vial and capped. The vial containing thefilm was heated to a temperature of 60° C. for one hour. The vial wasallowed to cool to room temperature, after which time the film samplewas removed and was rinsed twice with methanol. The rinsed film sampleswere then allowed to dry at room temperature. When a drop of water wasplaced on the film sample, the drop was observed to be rapidly (i.e.,nearly instantly) absorbed by the film sample. The average pore size andwater flux of the sample were determined as described above, and bothvalues were found to be essentially equivalent to those of DURAPORE “A”film.

Example 16

The average pore size and water flux of a sample of each of DURAPORE “A”film and DURAPORE “B” film was determined. A sample of DURAPORE “B” filmwas saturated with a 10 weight percent solution of SR344 in methanol andwas then irradiated with an electron beam at a dose of 20 kilograys(kGy). The sample was then rinsed three times with water and was placedin water that was heated to 70° C. for one hour. The sample was observedto be readily wetted by the water. The average pore size and water fluxof this sample were determined as described above, and both values werefound to be essentially equivalent to those of DURAPORE “A” film.

Examples 17-22

In Examples 17-22, samples of TIPS “A” film were saturated with SR344 orSR603 and were then irradiated with an electron beam as indicated inTable 3. In Table 3, the electron beam radiation dose is given withintegers separated by “+” to indicate that the same sample wassequentially irradiated (i.e., irradiated more than once) at the dosegiven in the Table. After the samples were irradiated, the water flux ofa first piece of the sample was measured as described above. A secondpiece of the sample was heated in an oven at 60° C. for one hour andthen the sample was allowed to cool to room temperature. The water fluxof the second piece of sample was then measured as described above. Thedata are given in Table 3. In Table 3, the term “Monomer” refers to thePEG diacrylate (SR344) or PEG dimethacrylate (SR603) that was used tosaturate the film samples, the term “Dose” refers to the electron beamradiation dose in kGy, the term “Flux 1” refers to the water flux time(in seconds) of the first piece of sample, and the term “Flux 2” refersto the water flux time (in seconds) of the second piece of sample (i.e.,the piece that was heated at 60° C. for one hour).

TABLE 3 Data for Examples 17-22 Dose Flux 1 Flux 2 Example Monomer (kGy)(seconds) (seconds) 17 20% SR603 60 28.8 32.0 18 20% SR603 20 + 40 22.419.5 19 20% SR603 40 26.3 18.4 20 20% SR603 20 + 20 + 21.6 18.5 20 2120% SR603 20 + 20 24.8 20.7 22 20% SR344 20 + 20 + 28.6 23.0 20

Examples 23-26

In Examples 23, 25, and 26, samples of TIPS “A” film were saturated witha 10 weight percent solution of SR344 in methanol. In Example 24, asample of TIPS “A” film was saturated with a 20 weight percent solutionof SR603 in methanol. Each of the samples was irradiated with anelectron beam at a dose of 20 kGy, as indicated in Table 4. Each samplewas then washed with methanol and was allowed to dry. The films ofExamples 24 and 26 were then saturated with a 20 weight percent solutionof CD553 in methanol. The film of Example 25 was then saturated with a10 weight percent solution of CD553 in methanol. The film of Example 23was then saturated with a 20 weight percent solution of SR603 inmethanol. The films of Examples 24-26 were then irradiated an electronbeam at a dose of 20 kGy, as indicated in Table 4. The film of Example23 was then irradiated to an electron beam dose of 40 kGy, as indicatedin Table 4. In Table 4, the designations of the two monomers used ineach of Examples 23-26 are separated by “/”. In Table 4, the electronbeam doses that are listed for each irradiation step are separated by“−”. Each sample was then washed with methanol and was allowed to dry.After the samples were irradiated, the water flux of a first piece ofthe sample was measured as described above. A second piece of the samplewas heated in an oven at 60° C. for one hour and then the sample wasallowed to cool to room temperature. The water flux of the second pieceof sample was then measured as described above. The data are given inTable 4. In Table 4, the term “Monomer” refers to the PEG 400 diacrylate(SR344) or PEG 400 dimethacrylate (SR603) that was used to saturate thefilm samples, the term “Dose” refers to the electron beam radiation dosein kGy, the term “Flux 1” refers to the water flux time (in seconds) ofthe first piece of sample, and the term “Flux 2” refers to the waterflux time (in seconds) of the second piece of sample (i.e., the piecethat was heated at 60° C. for one hour).

TABLE 4 Data for Examples 23-26 Dose Flux 1 Flux 2 Example Monomer kGy(seconds) (seconds) 23 10% SR344/20% SR603 20-40 19.0 32.0 24 20%SR603/20% CD553 20-20 29.5 21.4 25 10% SR344/10% CD553 20-20 28.4 23.526 10% SR344/20% CD553 20-20 28.6 21.2

Example 27

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then allowed to dry atroom temperature. The film sample was then saturated with a 20 weightpercent solution of GMA in methanol and was again irradiated with anelectron beam dose of 40 kilograys (kGy). The sample was then extractedwith MEK and then with water and was allowed to dry at room temperature.A portion of the sample was then saturated with a 20% aqueous solutionof urea and heated in an oven at a temperature of 60° C. for 45 minutes.The film sample was removed and was rinsed twice with water and wasallowed to dry at room temperature. The water flux of the sample wasthen measured as described above and was found to be 15.9 seconds.

Example 28

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of GMA in methanol and was then irradiated with an electronbeam dose of 40 kilograys (kGy). The sample was then extracted with MEKand was allowed to dry at room temperature. The non-water absorbent filmsample was then saturated with JEFFAMINE XTJ-504 and the film was thenplaced in a glass vial and capped. The vial containing the film washeated to a temperature of 60° C. for one hour. The vial was allowed tocool to room temperature, after which time the film sample was removedand was rinsed twice with methanol. The rinsed film sample was thenallowed to dry at room temperature. When a drop of water was placed onthe film sample, the drop was observed to be rapidly (i.e., nearlyinstantly) absorbed by the film sample. The water flux of the sample wasthen measured as described above and was found to be 15.5 seconds.

Example 29

A sample of TIPS “A” film was saturated with a 20 weight percentsolution of GMA in methanol and was irradiated with an electron beamdose of 40 kilograys (kGy). The sample was then extracted with MEK andwas allowed to dry at room temperature. The film was then saturated withDETA and the film was then placed in an oven at a temperature of 60° C.for one hour. The sample was allowed to cool to room temperature, afterwhich time the film sample was rinsed twice with methanol. The rinsedfilm samples were then allowed to dry at room temperature. The waterflux of the sample was then measured as described above and was found tobe 16.0 seconds.

Comparative Example 6

The water flux of a sample of TIPS “B” film was measured as describedabove and was found to be greater than 6 minutes.

Example 30

A sample of TIPS “B” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then rinsed withmethanol and was allowed to dry at room temperature. The water flux of afirst portion of the sample was measured as described above and wasfound to be approximately 5 minutes. A second portion of the sample washeated in an oven at 60° C. for one hour and then the sample was allowedto cool to room temperature. The water flux of this second portion ofthe sample was then measured as described above and was found to beapproximately 3.5 minutes.

Example 31

The film sample of Example 30 that was allowed to dry at roomtemperature was saturated with a 20 weight percent solution of GMA inmethanol and was irradiated with an electron beam dose of 40 kilograys(kGy). The sample was then extracted with MEK and was allowed to dry atroom temperature. A portion of the sample was then saturated withJEFFAMINE XTJ-504 and the film was then placed in a ZIPLOC bag, whichwas sealed and was placed in a water bath at a temperature of 60° C. forone hour. The bag containing the sample was allowed to cool to roomtemperature, after which time the film sample was removed and was rinsedtwice with methanol and was allowed to dry at room temperature. Thewater flux of the sample was then measured as described above and wasfound to be approximately 2.5 minutes.

Example 32

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then rinsed three timeswith water and was allowed to dry at room temperature. The film samplewas then saturated with a 20 weight percent solution of GMA in methanoland was irradiated with an electron beam dose of 20 kilograys (kGy). Thesample was then extracted with MEK and then with water and was allowedto dry at room temperature. A piece of the sample was then saturatedwith a mixture of 16.7 weight percent DETA and 16.7 JEFFAMINE XTJ-504 inwater, the film was heated in an oven at a temperature of 90° C. for 15minutes. The film was rinsed twice with water and allowed to dry at roomtemperature. The film sample was observed to be readily wetted by water.

Example 33

A sample of DURAPORE “B” film was treated essentially as described inExample 32. The film sample was observed to be readily wetted by water.

Example 34

A sample of TIPS “A” film was saturated with a 20 weight percentsolution of GMA in methanol and was irradiated with an electron beamdose of 40 kilograys (kGy). The sample was then extracted with MEK andwas allowed to dry at room temperature. A piece of the sample was thensaturated with a mixture of 16.7 weight percent DETA and 16.7 JEFFAMINEXTJ-504 in water, and the film was then placed in an oven at atemperature of 90° C. for 15 minutes. The sample was allowed to cool toroom temperature, after which time it was rinsed twice with water andwas allowed to dry at room temperature. The film sample was observed tobe readily wetted by water.

Comparative Example 7

A sample of TIPS “A” film was saturated with DETA. The film was thenheated in an oven at a temperature of 65° C. for 15 minutes. The filmsample was rinsed twice with water. The rinsed film sample was allowedto dry at room temperature. When a drop of water was placed on the filmsample, the drop was observed not to be absorbed by the film.

Example 35

A sample of hydrophilic EVOH film was saturated with a 20 weight percentsolution of APTAC in methanol and was then irradiated with an electronbeam dose of 40 kilograys (kGy). The sample was then rinsed three timeswith water and was allowed to dry at room temperature. The film samplewas observed to still be hydrophilic. A 1 weight percent aqueoussolution of Ponceau S dye was then passed through the film by mountingthe film in a holder on a filter flask and using vacuum to pull the dyesolution through the film. The film was then exhaustively washed withwater. The film was red in color after this washing step.

Comparative Example 8

A 1 weight percent aqueous solution of Ponceau S dye was passed throughEVOH film by mounting the film in a holder on a filter flask and usingvacuum to pull the dye solution through the film. The film was thenexhaustively washed with water. The film was not red in after thiswashing step.

Example 36

A sample of PES “A” film that takes about 8 seconds to wet through wassaturated with a 10 weight percent solution of SR344 in methanol and wasthen irradiated with an electron beam dose of 40 kilograys (kGy). Thesample was then rinsed with MEK and was then allowed to dry at roomtemperature. When a drop of water was placed on the film sample (shinnyside down—this film has sidedness in the form of a skin layer), the dropwas observed to be more rapidly (i.e., nearly instantly) absorbed by thefilm sample.

Example 37

A sample of PES “B” film was saturated with a 20 weight percent solutionof APTAC in methanol and was then irradiated with an electron beam doseof 40 kilograys (kGy). The sample was then rinsed three times with waterand was allowed to dry at room temperature. The film sample was observedto be readily wetted by water. A 1 weight percent aqueous solution ofPonceau S dye was then passed through the film by mounting the film in aholder on a filter flask and using vacuum to pull the dye solutionthrough the film. The film was then exhaustively washed with water. Thefilm was light red in color after this washing step. If a film samplehas a skin layer on one side, the skin layer is placed down in theholder for these tests.

Comparative Example 9

A 1 weight percent aqueous solution of Ponceau S dye was passed throughPES “B” film by mounting the film in a holder on a filter flask andusing vacuum to pull the dye solution through the film. The film wasthen exhaustively washed with water. The film was not red in color afterthis washing step.

Example 38

A sample of NYLAFLO film was saturated with a 20 weight percent solutionof APTAC in methanol and was then irradiated with an electron beam doseof 40 kilograys (kGy). The sample was then rinsed three times with waterand was allowed to dry at room temperature. The film sample was observedto be readily wetted by water. A 1 weight percent aqueous solution ofPonceau S dye was then passed through the film by mounting the film in aholder on a filter flask and using vacuum to pull the dye solutionthrough the film. The film was then exhaustively washed with water. Thefilm was red in color after this washing step.

Comparative Example 10

A 1 weight percent aqueous solution of Ponceau S dye was passed throughNYLAFLO film by mounting the film in a holder on a filter flask andusing vacuum to pull the dye solution through the film. The film wasthen exhaustively washed with water. The film was light pink in colorafter this washing step.

Example 39

A sample of TIPS “C” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 10 kilograys (kGy). The sample was then rinsed withmethanol and was then allowed to dry at room temperature. When a drop ofwater was placed on the film sample, the drop was observed to be rapidly(i.e., nearly instantly) absorbed by the film sample.

Example 40

A sample of TIPS “C” film was treated essentially as described inExample 39, except that the film was irradiated with an electron beamdose of 20 kilograys (kGy). When a drop of water was placed on the filmsample, the drop was observed to be rapidly (i.e., nearly instantly)absorbed by the film sample.

Example 41

A sample of TIPS “A” film was saturated with a 20 weight percentsolution of SR603 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then rinsed withmethanol and was then allowed to dry at room temperature. This film wasthen saturated with a solution of 20 weight percent AMPS in aqueousmethanol and was then irradiated with an electron beam dose of 30kilograys (kGy). The film was then rinsed with water and was allowed todry. When a drop of water was placed on the film sample, the drop wasobserved to be rapidly (i.e., nearly instantly) absorbed by the filmsample. A 1 weight percent aqueous solution of Methylene Blue dye wasthen passed through the film by mounting the film in a holder on afilter flask and using vacuum to pull the dye solution through the film.The film was then exhaustively washed with water. The film was blue incolor after this washing step.

Example 42

A sample of TIPS “A” film was saturated with a 20 weight percentsolution of SR603 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy). The sample was then rinsed withmethanol and was then allowed to dry at room temperature. This film wasthen saturated with a solution of 20 weight percent APTAC in aqueousmethanol and was then irradiated with an electron beam dose of 30kilograys (kGy). The film was then rinsed with water and was allowed todry. When a drop of water was placed on the film sample, the drop wasobserved to be rapidly (i.e., nearly instantly) absorbed by the filmsample. A 1 weight percent aqueous solution of Ponceau S dye (a red dye)was then passed through the film by mounting the film in a holder on afilter flask and using vacuum to pull the dye solution through the film.The film was then exhaustively washed with water. The film was red incolor after this washing step.

Example 43

A sample of TIPS “A” film was treated essentially as described inExample 42, except that AETAC was used in place of APTAC. When a drop ofwater was placed on the film sample, the drop was observed to be rapidly(i.e., nearly instantly) absorbed by the film sample. A 1 weight percentaqueous solution of Ponceau S dye was then passed through the film bymounting the film in a holder on a filter flask and using vacuum to pullthe dye solution through the film. The film was then exhaustively washedwith water. The film was red in color after this washing step.

Example 44

A sample of TIPS “A” film was saturated with a 20 weight percentsolution of GMA in methanol and was irradiated with an electron beamdose of 40 kilograys (kGy). The sample was then extracted with MEK andwas allowed to dry at room temperature. A piece of the still hydrophobicsample was then saturated with a 20 weight percent solution of JEFFAMINET-5000 in MEK, and the film was then placed in a glass vial and capped.The vial containing the wet film was heated to a temperature of 60° C.for 45 minutes. The vial was allowed to cool to room temperature, afterwhich time the film sample was removed and was rinsed with water andthen with 2-propanol and was allowed to dry. The film sample wasobserved to be readily wetted by water.

Example 45

A sample of PVDF non-woven film, prepared according to PreparativeExample 1, was saturated with a 20 weight percent solution of APTAC inaqueous methanol and was then irradiated with an electron beam dose of40 kilograys (kGy). The sample was then washed with water and wasallowed to dry at room temperature. A 1 weight percent aqueous solutionof Ponceau S dye was then passed through the film by mounting the filmin a holder on a filter flask and using vacuum to pull the dye solutionthrough the film. The nonwoven film was then exhaustively washed withwater. The film was red in color after this washing step.

Example 46

A sample of TIPS “C” film was treated essentially as described inExample 35 except that the film was saturated with isopropanol beforethe Ponceau S dye solution was flushed through the film. After the filmwas then exhaustively flushed with water, the film was pink in color.

Example 47

A sample of TIPS “A” film was saturated with a 10 weight percentsolution of SR344 in methanol and was then irradiated with an electronbeam dose of 20 kilograys (kGy) in the manner described above. The filmsample was then saturated with a 20 weight percent solution of GMA inmethanol and was again irradiated with an electron beam to a dose of 40kilograys (kGy) in the manner described above. The film sample was thenplaced in a jar and immersed in a solution of 10% sodium sulfite, 15%2-isopropanol and 75% water. The jar was capped and heated to atemperature of 80° C. for 90 minutes. The jar was allowed to cool toroom temperature, after which time the film sample was removed and wasrinsed with water and allowed to dry. When a drop of water was placed onthe film sample, the drop was observed to be rapidly (i.e., nearlyinstantly) absorbed by the film sample. The water flux of the sample wasthen measured as described above and was found to be 23 seconds. A 1weight percent aqueous solution of Methylene Blue dye was then passedthrough the film by mounting the film in a holder on a filter flask andusing vacuum to pull the dye solution through the film. The film wasthen exhaustively washed with water. The film was blue in color afterthis washing step.

Example 48

In a nitrogen-filled glove box, a sample of TIPS “D” film was saturatedwith 2-vinyl-4,4-dimethylazlactone (available from TCI America,Portland, Oreg.). The saturated film was transferred to a ZIPLOC bagwhich was then sealed and removed from the glove box. The film sample inthe ZIPLOC bag was then irradiated with an electron beam dose of 40kilograys (kGy). The film sample was then removed from the bag and wasallowed to dry at room temperature. The film sample was then analyzed byFTIR. The infrared spectrum showed peaks that indicated that theazlactone moiety was present on the surface of the film.

Example 49

A sample of TIPS “D” film was treated essentially as described inExample 48, expect that 2-isocyanatoethyl methacrylate was used insteadof 2-vinyl-4,4-dimethylazlactone. The film sample was then analyzed byFTIR. The infrared spectrum showed peaks that indicated that isocyanatogroups were present on the surface of the film.

Example 50

A sample of PVDF nonwoven web, prepared according to Preparative Example2, was imbibed and fully saturated with a solution comprising 68%methanol, 8% water and 24% (3-acrylamidopropyl)trimethylammoniumchloride (APTAC available from Aldrich) and sandwiched between 100 μmthick polyethylene terephthalate (PET) cover sheets. The sample sandwichwas processed through an electron beam at a dose of 40 kilograys (kGy)(@ 300 kv) and allowed to remain closed for at least 1 minute afterirradiation. The sandwich was opened and the treated web was removed andrinsed 3 times in a tray of deionized (DI) water.

Functionality testing was conducted by placing a 47 mm sized disk of thetreated nonwoven web in a 20 ml vial with 16 ml of a 0.0032 M solutionof METANIL Yellow dye (available from Alfa Aesar (Ward Hill, Mass.)) and4 ml of DI water. The vials were agitated by rocking for 12 hours toensure the dye solution was in equilibrium with the treated disk. Theresult was an orange web where the negative dye was bound to thepositively charged APTAC grafted EVOH nonwoven and the remaining dyesolution in the vial was almost clear. The dye was bound to the graftednonwoven fibers. The control EVOH film without the APTAC graft wastested in the same manner. Little or no binding occurred based on theintensity of the dye color remaining in solution. The bound dye does notrinse off the web with water.

Example 51

A sample of PVDF nonwoven web, prepared according to Preparative Example2, was imbibed and fully saturated with a solution comprising 52%methanol, 24% water and 24% (2-acrylamido-2-methylpropanesulfonic acidsodium salt (AMPS) and sandwiched between 100 μm thick PET cover sheets.The sample sandwich was processed through an electron beam at a dose of40 kilograys (kGy) (@ 300 kv) and allowed to remain closed for at least1 minute after irradiation. The sandwich was opened and the treated webremoved and rinsed 3 times in a tray of DI water.

Functionality testing was conducted by placing a 47 mm sized disk of thetreated nonwoven web in a 20 ml vial with 16 ml of a 0.0032 M solutionof quinaldine red dye (available from TCI (Tokyo, Japan)) and 4 ml of DIwater. The vials were agitated by rocking for 12 hours to ensure the dyesolution was in equilibrium with the treated disk. The result was apurple web where the positive dye was bound to the negatively chargedAMPS grafted EVOH nonwoven and the remaining dye solution was almostclear. The dye was bound to the nonwoven coated fibers. The control EVOHfilm without the AMPS graft was tested in the same manner and exhibitedlittle or no dye binding based on the intensity of the dye colorremaining in solution. The bound dye does not rinse off the web withwater.

Example 52

A sample of TIPS “A” film was used except the film was made by castingthe melt onto the patterned chrome casting wheel, which had been coatedwith a thin layer of triacetin to minimize the degree of “skinning” thatcan occur when the melt is cast directly onto a metal surface resultingin the surface of the melt crystallizing faster than the bulk of themelt (i.e. skinning). The film thickness was about 56 μm. A slight skinon the film can limit the amount of APTAC monomer that can be graftedbefore a reduction in flux occurs.

The film was saturated with a 10 wt % solution of SR344 in methanol,sandwiched between 100 μm thick PET cover sheets, and then irradiatedwith an electron beam dose of 20 kilograys (kGy) in the manner aspreviously described. The sample sandwich was opened after waiting atleast one minute and the film then removed and rinsed with DI watertwice (in a tray) and allowed to dry. The film sample was then saturatedwith a 24% solution of APTAC (75% monomer in water) in methanol and wasagain irradiated with an electron beam to a dose of 40 kilograys (kGy)in the manner described before. The sandwich was opened after waiting atleast one minute and the film rinsed with DI water three times (in atray) and allowed to air dry.

Functionality testing was conducted by placing a 47 mm sized disk of thetreated PVDF web in a 8 ml vial with 5 ml of a 0.0016 M solution ofMETANIL Yellow dye (available from Alfa Aesar (Ward Hill, Mass.)) and 3ml of DI water. The vial was agitated by rocking for 12 hours to ensurethe dye solution was in equilibrium with the treated disk. The resultwas a green tinted film (originally blue) where the negative dye wasbound to the positively charged APTAC grafted PVDF film and the dyesolution was almost clear. The dye was bound to the membrane and did notrinse off with water.

While the specification has been described in detail with respect tospecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

1. A method of making a functionalized substrate, the method comprisesthe steps of: providing a porous base substrate having interstitial andouter surfaces; imbibing the porous base substrate with a first solutionto form an imbibed porous base substrate, the first solution comprisingat least one grafting monomer having (a) a free-radically polymerizablegroup and (b) an additional functional group comprising an ethylenicallyunsaturated group, epoxy group, azlactone group, isocyanate group, orcombination thereof, and (c) optionally a grafting monomer having afree-radically polymerizable group and an alkylene oxide group; exposingthe imbibed porous base substrate to a controlled amount of electronbeam radiation so as to form a first functionalized substrate comprisinggrafted species attached to the surfaces of the porous base substrate,wherein at least one of the grafted species comprises the epoxy group,azlactone group, isocyanate group, imbibing the first functionalizedsubstrate with a second solution comprising at least one nucleophiliccompound comprising at least one nucleophilic group; and exposing thefirst imbibed functionalized substrate to a controlled amount of heat soas to react the nucleophilic compound with the epoxy group, azlactonegroup, isocyanate group, or combination thereof.
 2. The method of claim1, wherein the first imbibing solution comprises a grafting monomerhaving a free-radically polymerizable group and an alkylene oxide group.3. The method of claim 1, wherein the porous base substrate ismicroporous.
 4. The method of claim 1, wherein the porous base substrateis selected from a porous membrane, porous non-woven web, or porousfiber.
 5. The method of claim 1, wherein the porous base substrate is amicroporous membrane or a nonwoven web that is hydrophobic.
 6. Themethod of claim 1, wherein the porous base substrate is hydrophobic andthe functionalized substrate is hydrophilic.
 7. The method of claim 1,further comprising the step of exposing the functionalized substrate toa heat cycle at 30° C. or higher.
 8. The method of claim 1, wherein thegrafting monomer having a free-radically polymerizable group and analkylene oxide group comprises a polyalkylene glycol di(methacrylate).9. The method of claim 1, wherein the imbibing solution comprises apolyalkylene glycol di(meth)acrylate and a glycidyl (meth)acrylate,isocyanatoalkyl (meth)acrylate, or vinyl azlactone.
 10. The method ofclaim 1, wherein the nucleophilic compound comprises a nucleophilicgroup comprising at least one primary amino group, secondary aminogroup, hydroxy or combination thereof.
 11. The method of claim 10,wherein the nucleophilic compound has a plurality of nucleophilic groupsthat react to crosslink at least two grafted species.
 12. The method ofclaim 11, wherein the nucleophilic compound comprises at least twoprimary amino groups and a polyalkylene oxide group.
 13. The method ofclaim 1 comprising the step of imbibing the porous bases substrate witha grafting monomer having (a) a free-radically polymerizable group and(b) an ionic group.
 14. The method of claim 1 comprising the step ofimbibing the porous bases substrate with a grafting monomer having (a) afree-radically polymerizable group and (b) an ethylenically unsaturatedgroup.
 15. The method of claim 1, wherein the porous base substrate is ahydrophobic microporous membrane having an initial average pore size andthe functionalized substrate is hydrophilic microporous membrane havinga final average pore size that is larger than the initial average poresize of the porous base substrate.
 16. The method of claim 15, whereinthe hydrophobic microporous membrane is formed by a thermally-inducedphase separation (TIPS) method.
 17. The method of claim 16, wherein thehydrophobic microporous membrane comprises poly(vinylidene fluoride)formed by a thermally-induced phase separation (TIPS) method.
 18. Themethod of claim 1, wherein the controlled amount of electron beamradiation exposure comprises a dosage of 20 kGy to 40 kGy.
 19. A methodof making a functionalized substrate, the method comprises the steps of:providing a porous base substrate having interstitial and outersurfaces; imbibing the porous base substrate with a first solution toform an imbibed porous base substrate, the first solution comprising atleast one grafting monomer having (a) a free-radically polymerizablegroup and (b) an additional functional group comprising an ethylenicallyunsaturated group, epoxy group, azlactone group, isocyanate group, orcombination thereof, and (c) optionally a grafting monomer having afree-radically polymerizable group and an alkylene oxide group;positioning the imbibed porous base substrate between a removablecarrier layer and a removable cover layer to form a multilayerstructure; exposing the multilayer structure to a controlled amount ofelectron beam radiation so as to form a functionalized substratepositioned between the removable carrier layer and the removable coverlayer, the functionalized substrate comprising grafted species attachedto the surfaces of the porous base substrate, wherein at least one ofthe grafted species comprises the additional functional group; andremoving the carrier layer and cover layers from the multilayerstructure.